Jeremy Corbyn has been sworn in by The Queen as a member of the Privy Council, the elite group of senior politicians who are entitled to confidential security briefings.
Asked whether the Labour leader had followed usual Royal protocol and knelt before Her Majesty and kissed her hand, a spokesman refused to answer directly and simply told HuffPostUK: “He complied with the normal processes.”
HuffPost understands that the Palace had suggested beforehand that kneeling was not essential to the process.
In an ITV News interview before the event - but released after it - Mr Corbyn said: "I don't expect to be kneeling at all. I expect to be nominated to the Privy Council and that's it."
A lifelong Republican, Mr Corbyn arrived at Buckingham Palace in a chauffeur-driven people carrier, but insisted on sitting in the front seat rather than the back.
He is famously uncomfortable with the more ceremonial aspects of his role as Leader of Her Majesty's Loyal Opposition, but the short meeting was a formality that now means he can be briefed on matters of national security.
“Jeremy is now a member of the Privy Council," a spokeswoman said after the ceremony, which ex-ministers have said involves kneeling on a stool or chair, kissing the Monarch's hand, and swearing an oath of allegiance.
Mr Corbyn also has the title 'The Right Honourable', a prefix he has in the past complained has given undeserved higher ranking to senior MPs in Commons debates.
In a BBC interview in September, Mr Corbyn refused to say if he would kneel before the Queen and claimed: '"I think there are some things that ought to change in our society and maybe that’s one of them."
Mr Corbyn has come under fire in the past for failing to sing the National Anthem at a Whitehall ceremony, but his allies hit back at claims that he did not 'bow' at the Cenotaph for Remembrance Sunday.
Other Republican MPs have found canny ways of combining their views with the ceremony, with the late Tony Benn famously writing in his diaries that he kissed his own thumb rather than the Queen's hand.
But others have just agreed to go along with the protocol, despite their reservations.
John Prescott, who only joined the Privy Council after told to refuse membership so would bar him from important briefings, has revealed the protocol involved in the process.
He told the BBC: "When I was first asked to join the Privy Council by John Major I said I didn’t want to do it, he said 'why?' [I said] because you have to kneel and kiss her hand.
"I didn’t want to do that, I thought it was a stupid arrangement, I still think it should go. But you don’t do that; you hop. Get into hopping. You hop from one chair to another and brush your lips lightly across her hand.
"But you don’t do that – you hop. Get into hopping. You hop from one chair to another and brush your lips lightly across her hand. But don’t forget this, they told me when I said ‘no’, you wont get the same information Blair gets.
"Because they only give information from the Queen’s council on that. That is quite wrong, you can’t refuse a member who is elected simply because of some royal prerogative.”
In a BBC regional news interview before the event, the Labour leader said: "apparently it's going to be a very normal kind of occasion and I will be appointed".
ITV News's Chris Ship tweeted that Mr Corbyn had been determined not to kneel.
Jeremy Corbyn has told us 'I don't expect to be kneeling at all' when he meets to Queen for his Privy Council appointment tonight— Chris Ship (@chrisshipitv) November 11, 2015
Although some newspapers have criticised Mr Corbyn for not attending his first available Privy Council appointment, he in fact attended a month faster than David Cameron did in 2005.
The Privy Council is one of the most ancient political bodies in the UK and formally advises the Monarch as she carries out duties as head of state.
It dates from Norman times, when the monarch met in private - the derivation of the word 'Privy' - a group of trusted counsellors who pre-dated the Cabinet of ministers.
Meetings - which take place with ministers standing up - are normally held monthly at Buckingham Palace or Windsor Castle. There is a total of more than 500 privy counsellors, but many are former ministers and hold the title formally.
Commons leader Chris Grayling is the Lord President of the Council.