At a recent summer drinks party for high-profile Labour supporters, it wasn't Ed Miliband's speech that wowed the crowd. It was his wife's.
"I am trying to change the world through the law," Justine Thornton, aka Mrs Miliband, told the assembled luminaries in the sun-lit courtyard of Mary Ward House in central London.
Her speech was a combination of charming tributes to her husband, passionate declamations on the need to change the way politics is conducted and, of course, the obligatory, self-deprecating anecdotes about life as a political leader's wife. Thornton, a Cambridge-educated barrister, told an amusing story about how she and her husband, only a few weeks ago, had been frantically trying to find a bottle of wine in their kitchen to serve to a surprise house guest, Helle Thorning-Schmidt, who just happens to be the prime minister of Denmark (as well as the wife of Labour parliamentary candidate Stephen Kinnock, son of Neil). "It was more Fawlty Towers than Borgen," she deadpanned.
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Members of the audience, which included actor Ross Kemp, TV presenter Fiona Phillips and Hollywood director Paul Greengrass, later described her address - delivered, like a true Miliband, without notes - as "inspirational", "from the heart" and "pack[ing] a punch".
It hasn't been easy for Thornton to play the part that is expected of her by politicians and pundits alike. Shortly after Miliband won the leadership of his party, Thornton logged onto Amazon to look for books that might help her adapt to her new role. But all her searches produced were links to DVD box sets of the hit US legal drama, 'The Good Wife'.
The role of politician's wife is "not a role I applied for, darling," she said, turning to grin at her husband who watched on with a mix of awe and pride. Nevertheless, Thornton continued, she intended to be at his side throughout the election campaign, ready to help take on her husband's vast army of doubters, critics and opponents.
Ten months out from the general election, and with Labour's poll lead narrowing, Miliband needs all the assistance he can get - and from every possible quarter. In recent weeks, the Leader of the Opposition has been battered over his image, with polls showing voters think he is "weird" and fellow Labour MPs, such as the former home secretary Alan Johnson, claiming to find little warmth or enthusiasm for him on the doorstep. Then there was the indignity of being photographed trying - and failing - to eat a bacon sandwich for breakfast, as well as his bizarre decision to pose for the cameras alongside a copy of The Sun.
In contrast, standing next to his wife, on the courtyard steps at Mary Ward House, Miliband looked relaxed, personable.. normal. Over the next few months, according to senior Labour sources, we will start to see the confident and self-assured Thornton emerge from the shadows; we will see Ed and Justine together in public, at events, on the campaign trail, in the media. Her chief task, they whisper, will be to humanise him, to anchor him in the "real world", not the "wonk world".
So, could Mrs Miliband be the Labour leader's secret weapon?
Born in 1970 in Manchester but raised in Nottingham, Justine Thornton attended local comprehensive West Bridgford School, where former pupils include the Oscar-nominated British actress Samantha Morton.
Thornton herself had the acting bug and came to public attention as a teenage actor appearing in the Central Television drama 'Hardwicke House'. She played rebellious schoolgirl Erica who called Geoffrey Howe, then Margaret Thatcher's foreign secretary, a "fascist" in the pilot show, though the series was soon cancelled after a public outcry over its "comic violence and portrayal of dysfunctional pupils," according to the Daily Telegraph.
Thornton also starred in ITV's 'Dramarama', before starting to lose interest in acting. Ferociously intelligent, the teenaged Thornton wanted to focus on her academic career.
She achieved straight As in her maths, English and history A-levels and secured a place at Robinson College, Cambridge, where she read law. Graduating in 1992, Thornton was called to the bar two years later where she met, and struck up a friendship with, Frances Osborne - now the wife of the chancellor - with whom she went backpacking across South America. (“I’m immensely fond of Justine,” Osborne told the Times in 2012, adding that the two women were part of a "common gang" of MPs' spouses.)
In 2004, Thornton met Miliband at a dinner party in London. The Labour Party special adviser, who had only just returned from a two-year sabbatical at Harvard University, struck up a conversation with the sharp, witty and attractive lawyer and the two hit it off. It was a meeting of minds - a friend of Justine's once described to me the latter's excitement after meeting Miliband as "gosh how fascinating, he's really clever" rather than "gosh how handsome".
In a speech to Labour activists in 2013, Thornton herself recalled how it was local Labour activists in Doncaster, from where Miliband was trying to get elected in 2005, who first guessed that she and the Labour candidate had fallen for each other. Thornton said she had travelled up from London to Doncaster to help Miliband set up for a party meeting when an activist said to her: "That's a very long way to come to move chairs, are you sure you're just friends?" According to Thornton, the activist was "clearly very astute and realised before we did I think."
Miliband himself told Radio 4's 'Desert Island Discs' in 2013 that the reason he was such a fan of the Robbie Williams song 'Angels' was because he had realised he was in love with Thornton while the pair watched Williams sing it live on stage during the Live 8 concert in Hyde Park in July 2005.
For Miliband, a former special adviser to Gordon Brown and Harriet Harman, who had been raised in the über-ideological home of a high-profile Marxist academic, Thornton was a breath of fresh air. She brought some much-needed fun and colour to his serious, politics and policy-obsessed life - and, by all accounts, still does.
Friends of the Labour leader's wife speak, for instance, of her "sense of adventure". In 2005, only a few months after she started dating Miliband, Thornton joined a friend and fellow barrister, Quincy Whittaker, on a climb up the 4,167-metre Mount Toubkal in Morocco - the highest peak in the Atlas Mountains. Later, when Whitaker suggested they visit India, Thornton proposed they go "via Afghanistan".
Nevertheless, the adventurous Thornton has also had to do much of the heavy lifting in her relationship with Miliband, distracted (obsessed?) as the latter is by the all-consuming worlds of politics and government.
When the pair combined their financial resources to buy their north London townhouse for £1.6million in 2009, it was Thornton's name, and not Miliband's, that went on the property deed.
When their first child Daniel was born in 2009, Thornton registered the birth but wasn't able to add both parents' names because they weren't married. Miliband, it later turned out, was "too busy" to get round to going to the registry office in person and adding his name to the certificate.
He was also, it seems, "too busy" to get married to Thornton, becoming the first unmarried man to become leader of the Labour Party in September 2010.
In May 2011, the couple finally married in a small, very private ceremony, and with an emotional Miliband reducing his new wife to tears by telling her she was his "rock" and "the most beautiful, generous and kind person that I've ever met in my life".
When the time came for her own speech, Thornton told guests at the wedding: "When I was growing up I thought when I was 30 I would be married and have two kids. It might be a decade late but it was worth the wait for Ed."
It is, in a sense, remarkable that we have so seen so little of the eloquent and charming Thornton over the past four years. She is on the radar of only a handful of journalists; few members of the public would be able to identify her if shown a picture of the Labour leader's wife.
Yet, in an age of 24-hour news channels and live blogs, politicians' spouses tend to find themselves under greater scrutiny than ever before. The high-powered careers of Thornton (environmental barrister), Samantha Cameron (former business executive) and Miriam González Durántez (City lawyer) help explain some of the interest - but equally explain why the wives themselves are so uninterested in playing ball with journalists and prefer to adopt lower profiles.
It is difficult to overstate the importance that Thornton gives to her own job, as a high-flying barrister specialising in environmental law. In an interview with Grazia magazine in 2012, Miliband joked that his wife considers him the third most important thing in her life, behind their two sons and her legal career.
"She works at one of the country's most eminent chambers," says a member of the shadow cabinet, pointing to her position at Thirty Nine Essex Street, where she is believed to earn around £200,000 a year - compared to Miliband's £130,000 salary as leader of the opposition . "She's very impressive."
Leading legal directories such as Chambers & Partners and Legal 500 agree with the shadow minister's assessment, regularly referring to Thornton as, among other things, "very calm, focused and knowledgeable", "extremely bright [and] hardworking", a "first-class" advocate who "shows considerable attention to detail, commitment to the cause and great knowledge".
As the partner of a top politician, however, she has had to pick her cases with care. In March 2009, when Miliband was energy and climate change secretary in the Gordon Brown government, Thornton found herself embroiled in a 'conflict of interest' row when it emerged that she was representing energy company E.ON as it tried to win the right to build a series of coal and nuclear powered stations worth more than £20 billion. A departmental spokesman for Miliband was forced to remind the press that Thornton had not "acted for or against the department and will not receive or accept any such work in the future".
Perhaps, then, it is unfair to say she has put her career ahead of his. Indeed Miliband has said that his wife often jokes with him that she could have had "an easy life married to somebody else but it would have been a less interesting life".
A working mum, Thornton tells friends she values her privacy and, especially, the privacy of her kids - though the Labour leader's wife has, on occasion, agreed to do photo shoots with Daniel, aged 5, and Samuel, aged 3. She is still feeling her way towards an appropriate and - the cynics would say - mutually-beneficial relationship with the the press corps.
Can we expect her to see her pop up on the 'This Morning' couch or on the 'Loose Women' panel in the run-up to the general election next May? Maybe. Or she might, alternatively, decide to turn up on the Andrew Marr show or the Today programme to talk about the environment or the law.
"She will do her own thing, she won't be SamCam or Cherie," says a senior Labour source. "Justine is her own woman."
"I think she could do more media, but not just as a wife," adds a shadow cabinet minister. " She has strong views; she's an independent-minded woman."
The big question, though, is this: will Thornton be able to help Miliband revive his plummeting poll ratings?
According to a member of the Labour leader's inner circle, the comprehensive-educated Thornton, with her non-political, provincial background, "roots him in real life". She "connects Ed to the best part of himself," says the source.
In internal discussions, party strategists are said to refer to Thornton as "the best validator and authenticator" of Miliband and his 'One Nation', pro-'squeezed middle' message.
Those same strategists have secretly planned a bigger role for Thornton in the run-up to the general election - both during the Scottish referendum campaign over the summer and, in particular, at the party's annual conference in Manchester in September.
So far, all three leaders' wives have consistently refused to introduce their husbands at party conference, despite Sarah Brown having famously introduced husband Gordon at the Labour conference in 2009 as "my hero".
At Labour's conference in Brighton in 2013, Miliband told a TV interviewer that Thornton "has got a full-time job.. we are not bringing her on to introduce me at conference, I can assure you of that".
Whether he will make the same assurance this time round is another matter. Speculation is rife amongst some senior Labour figures that Thornton could give a 'game-changing' speech to introduce Miliband at this year's annual conference in September - the last such conference before the general election next May.
If Thornton does decide to speak ahead of Miliband in Manchester, as she did in Mary Ward House, she'll eschew corniness. "That's not Justine's style," says a member of the shadow cabinet. "The [Sarah Brown] 'hero' stuff was awful."
As an indication of how seriously Thornton takes her (rare) public appearances, it is worth recalling the irritated remark she made to a group of Labour supporters in Brighton last year. "All you'll know about me this year is the make of the dress I wear for Ed's speech on Tuesday," she told Young Labour activists. "I am in fact more than a dress."
Sceptics suggest 'upgrading' Thornton's role, and giving her a bigger profile, either at conference or on the campaign trail, will have little effect on the result of the next election. Pollster Peter Kellner, chairman of YouGov, tells me that "wives (and husbands) have little impact on the fortunes of political leaders, in Britain anyway". Kellner adds: "Two wives who had a positive image were, and are, Glenys Kinnock and Sarah Brown. They may have enhanced their husband's standing inside their own party; but as neither of their husbands won an election, it's hard to sustain the argument that they were vote winners."
Perhaps. But even if Thornton's only contribution in the coming months is to help Miliband get permission to be heard - as a normal, middle-class family man, 'rooted in real life', rather than as a weird, out-of-touch wonk, rooted in Westminster - Labour strategists will conclude that it will have been worth it.
And, as Damien Lyons Lowe, of the polling firm Survation, says: "If Ed Miliband presented himself more as a family man, a father, a husband - sending signals of someone in touch with life outside of politics, it's possible this could improve his personal ratings."
It would be a mistake to underestimate Thornton's commitment to the Miliband - and, by extension, Labour - cause. She is, in fact, as quietly ruthless and steely as her husband. During the leadership campaign in 2010, Thornton is reported to have told friends that she was more worried about her partner's political prospects, than his sibling rivalry with David: "Ed has to win it, and then we can sort that out."
Miliband refers to her as his "best counsel", and speaking to friends of both the Labour leader and his wife (then girlfriend) for our biography of him in 2011, my co-author James Macintyre and I discovered just how much of a "rock" Thornton is for Miliband. She advises, supports, bolsters, cheerleads. All of Miliband's big political moves - from his decision to challenge brother David for the party leadership in 2010 to his decision to challenge the Daily Mail's Paul Dacre over the legacy of his late father Ralph in 2013 - have been made only after long and intense discussions with Thornton. ("Life's an adventure," she is said to have replied, when Miliband asked her whether he should run for leader, "and you've got to seize the day.")
One friend of both Ed and Justine has talked about "their strikingly consensual relationship.. It is so equal: neither dominates at all." Other friends who we spoke to for our biography described Thornton as, among other things, "a great political wife, because while everyone is talking she just gets on with things"; a partner who "is engaged with [Miliband's] political life but easily his greatest refuge from it too"; and the person who "encourages him to trust his instincts".
Thornton, according to a shadow minister who has known the couple of several years, is very much on the centre-left and a keen supporter of Miliband's "responsible capitalism" agenda. "She's a political soulmate," says the shadow minister.
She also keeps him "grounded", to quote one of Miliband's former girlfriends, and is a reminder to the public that the Labour leader isn't just a professional politician, a wonk who obsesses over inequality and redistribution. He happens to be a proud husband and father too; Miliband has a wife and two kids who love and adore him as a person, not as a politician.
Normality is the keyword. "While Glenys at least was a political activist," Neil Kinnock, the former Labour leader, once reminded me, "Justine just has a totally normal background."
Will her "normal background" aid and abet the Leader of the Opposition in his mission to convince sceptical voters that he is on their side, understands their concerns and plans to fight on their behalf - if, that is, they decide to put him (and his wife) in Number 10 next May?
Over the next 10 months, Thornton will be on the campaign trail and will be speaking out much more often - regardless of how many critical pieces the the tabloids decide to run on her clothing or her career. "She regards it as a price she has to pay in order for Ed to do what he has to do," says a friend. Another adds: "She is not going to buckle no matter how difficult this gets."
Unlike a growing number of Labour MPs, Thornton believes in her husband - and believes he will win. She is convincned - as evidenced by her occasional public statements, as well as from the testimony of her friends and her husband's friends - that only Miliband can bring about radical change in the way the country is run.
Wrapping up her speech at Mary Ward House, Thornton said she and her husband wanted to make the next election about the need for "decency and principles in public life".
"That's why I am up for a fight," she told the crowd, "however nasty, however brutal."