Lauren and Beth Nicklinson are clearly much-loved daughters. Their father Tony has a photograph of them hugging that he keeps by his bed, and his eyes come alive when he sees them. The feeling is mutual and they talk fondly of the father who both insist they even liked during their teenage years.
'We were quite lucky, most teenagers don't want their friends round their dad but we were quite happy to bring friends home. Dad was loud and used to get involved and was a good laugh,' Lauren, 24, a public relations account manager, says with affection.
Beth, 23, who is studying for a degree in animal science, would give anything to hear one of his fatherly lectures again. She says sadly, 'I can't remember the sound of his voice. We used to hate his lectures when we were younger, but we kind of miss them now. He'd lecture us about working hard at school and warn us about boys, life preparing stuff.
'He was very involved in our lives and he always encouraged us with our school work. When we were kids, he always played with us or took us swimming. You couldn't fault him as a dad. He was brilliant.'
Their unconditional love is the reason they are supporting his brave court battle that will allow someone to kill him if he wins.
Tony Nicklinson, 58, is a relatively young man but has almost no quality of life. In June 2005, a massive stroke destroyed most of his brain stem leaving him paralysed but mentally alert suffering what is known as 'locked in syndrome'. He can do no more than move his eyes and head. He cannot talk, or feed himself and he communicates by blinking at a perspex letter board or via computer. His mouth hangs open and he dribbles constantly. Tony, who was always an active man, says: 'It's like being buried alive.'
The stroke happened while he was on a business trip to Athens. He had had a mini stroke 18 months earlier that had left him temporarily paralysed down one side. He had said then that he was afraid of not being able to live an active life and that he wouldn't want to live if he couldn't participate fully.
As he lay in intensive care in Athens, Tony's loved ones, wife Jane, a former nurse, and Lauren, told doctors that he wouldn't want to live in his condition, but medical staff made it clear that they could not stop giving him his life-saving medication. He was flown back to the UK in August but by December, the 6'4" former rugby playing, sky diving, engineer, was talking about suicide.
Beth says: 'As soon as he could communicate with us he decided this. The doctors thought he might adapt and he promised he would give it two years which he did, but he still felt the same.'
The family, who had been living in Dubai, moved into a specially adapted bungalow in Melksham, Wilts, in May 2006, and began a new way of life, accepting that the man they knew was gone. Tony however, found life unbearable and by 2007, was asking Jane if she could help him die.
Lauren remembers. 'I was 19 by that time and at university. I got a call from my mum, she was sobbing and she said that dad had asked her to help him die.
'When we were still in Athens, we spoke about it then and it was agreed that dad didn't want to live. He'd had a mini stroke 18 months earlier and had been paralysed down one side but he recovered. He said then that he was afraid of not being able to live an active life and he was frightened of that. He said then that he wouldn't want to live if he couldn't participate fully.
'We tried to get the doctors to take him off all his drugs to see if he would die, but they wouldn't take him off anything.' Tony himself began refusing all life saving medication back in 2007.
Both daughters are aware of the pro-life arguments and sympathise with the view that vulnerable people might be persuaded to end their lives not because they wanted to, but because it would suit relatives or carers. They find it endlessly frustrating that no one will listen to their father's point of view which is that that is not him.
Beth is adamant. 'Dad's of sound mind and he's lived like this for many years. He's a very intelligent man - he built us a computer. No one should be able to tell him that he should keep living if that's not what he wants.'
Lauren says. 'We understand the pro-life campaigners fears and concerns. We aren't campaigning for a massive change in the law that would mean all of a sudden anyone with a slight disability would be offered a lethal injection every time they went for a flu jab. People have said that that's what they think will happen and it's ridiculous, it's scaremongering.
'We're fighting for the right for Dad to die. Everything that we want we want to be regulated and to be strict, it shouldn't be easy. It should be really difficult to make sure that people aren't being coerced, that people are of sound mind and that it is what people want to do, but it should be possible.
'The people who voice those opinions are the ones who can still speak, they can push themselves round in a wheelchair, they have quality of life. That's not Dad. I don't think life should be forced on people if they don't want it.'
Tony himself couldn't be clearer. He says. 'My life has no meaning for me. I simply exist, kept alive because politicians are too cowardly to sort out the mess we have found ourselves in, mainly because of medicine's ability to make us live longer.
'The hearing will determine what sort of death awaits me. If I win, it means a pain free death. If I lose, I am faced with the choice of living until I die of natural causes or starving myself to death. Either option is not particularly inviting. So for me it is literally the difference between an unhappy life or a good death.
'Secondly, I want no one else to suffer the indignities I have had to suffer if they decide this sort of life is not for them.
'If I lose. my solicitor is prepared to take my case all the way to the European Court of Human Rights.'
So on Tuesday, with heavy hearts, the family will ask three judges at the High Court to allow any doctor helping Tony to die, to invoke the rarely used common law defence of 'necessity' against any murder charge. Necessity, was used by doctors seeking to separate conjoined twins Jodie and Mary who were joined at the abdomen. They knew the operation would result in the death of one twin and judges allowed it. The Ministry of Justice however say that in Mr Nicklinson's case, this would be 'crossing the rubicon.'
Currently, the law states that anyone assisting a suicide could receive a prison term of up to 14 years, murder carries a life sentence. The problem for Mr Nicklinson is that he has no terminal disease and although the courts have shown leniency in some assisted suicide cases in the past, they have involved people with terminal illnesses. Mr Nicklinson is also so severely disabled that no one would be able to assist his suicide, he would, to put it bluntly, have to be killed, which could amount to murder.
Lauren says, 'We have discussed mum taking dad to Dignitas or helping him to die here but they're not prepared to take the risk. Mum could face a life sentence in prison. Dad would rather spend 30 years locked in his own body than Mum spend 30 years in a jail cell. He would never let her do that, neither would I and neither would Beth.
'I could possibly cope with losing Dad but I couldn't cope with losing Mum as well.'
There have been cases of mercy killings where the courts have been lenient. Two years ago, Kay Gilderdale was cleared of attempting to murder her 31-year-old daughter Lynn, who had been disabled with ME from the age of 14 and simply wanted to die. Mr Justice Bean, the judge in the case, said the jury showed 'common sense and decency.'
Multiple sclerosis sufferer Debbie Purdy, won a victory in the House of Lords, after arguing that it was a breach of her human rights not to know whether her husband would be prosecuted if he helped her to end her life by taking her to Dignitas, the clinic in Switzerland that helps people to die.
The public are generally supportive and last week, the British Medical Journal published a poll that found 80% of the public support assisted dying.
On Monday, C4 will screen a special Dispatches programme at 8pm, called 'Let Our Dad Die,' in which Mr Nicklinson and his family take part. The programme looks intimately at the arguments from both sides. Most compelling is Mr Nicklinson himself, who allows us to see the full indignity of his life. He says. 'I would remind the judge that this shouldn't be about an arcane interpretation of the law, but it should be about the quality of life for a human, i.e. me.'
Mr Nicklinson's solicitor, Saimo Chahal, who also represented Debbie Purdy, says that they are not asking for legalised murder. 'We are asking that the courts look at this type of case on a case by case basis in the future. The courts would have to consider each case carefully and decide whether to make a declaration in that case.
'It's cruel to expect Mr Nicklinson to live in suspended animation for an indefinite period and the law is outdated and should be changed to accommodate cases like his.
'Modern medicine means that people can survive against all odds but they do not necessarily have any quality of life. It should be for them to decide whether they want to live or die.'
New evidence supporting Mr Nicklinson's plea will come from some surprising sources.
Dr Peter van Hasselt, a doctor from the Netherlands where euthanasia is legal will plead on his behalf, as will Alec Hutchins, a British father whose daughter had progressive multiple sclerosis and was forced to tip herself into a canal from her electric wheelchair to end her life. But most surprising is] Dr Stelios Doris, the Greek neurologist who helped save Mr Nicklinson's life. He now says: 'I wouldn't like for my worst enemy to stay alive in this condition. In a way we owe him. [To be allowed to die]. We made a mistake keeping him alive.'
Labour MP Lord Falconer, the Secretary of State for Justice, who chaired an independent commission on assisted dying disagrees. 'We want to protect people who could be over-persuaded to kill themselves.' Although confusingly he supports the case for assisted suicide but says legalised killing, 'is a step too far.'
Whatever the court's decision, which will take around a month to reach, the family will forever live with the consequences. Beth says. 'The end result will be bitter sweet. I'll either see my dad go when he chooses or I'll see him live like this for God knows how many years, which is also upsetting.'
Lauren adds. 'If he wins I'll be sad but I think I've grieved already. I've grieved for the fact that he wasn't able to drop me off at university, he couldn't come to my graduation, he never came to the pub with me to have a drink. He's never going to walk me down the aisle or teach my kids to play rugby.
'I'm more afraid of him living than dying. If he dies I will grieve but I will be OK after a few years. If we lose then he's going to be like this for the rest of his natural life. That's just too horrible to bear.'