Amid the neoclassical splendour of the ballroom in the Belgravia mansion that once belonged to the Guinness dynasty, the Irish ambassador's annual press party was going well.
By late in the evening on 5 December, a liveried footman at the London embassy had formally announced the arrival of about 300 guests, including dignitaries and power brokers such as the head of MI5, Dame Eliza Manningham-Buller, and the Dublin-born fashion designer Paul Costelloe.
Around the packed room with views over the gardens of Buckingham Palace, waiters circulated with trays of tempting canapés: rare roast beef in mini Yorkshire puddings, Irish smoked salmon on blinis.
And crucially, according to veterans of the embassy's legendary hospitality in London, the wine - not to mention the Guinness, gin and whiskey - flowed freely. Very freely.
As one guest put it: "It was as if the waiters had been given a quota of wine that they had to get rid of. It had the atmosphere of an 'everything must go' sale. They were very, very generous."
In the depths of such unbridled conviviality, the Right Reverend Tom Butler, Bishop of Southwark, was for those few hours at least just one among a throng of influential people having a good time. Albeit one clad in a cassock and dog collar.
But what followed is a tale of clerical amnesia and toe-curling allegations which have elevated the 66-year-old Anglican bishop from the status of cerebral prelate to Christmas party legend.
Dr Butler, a former electronics lecturer and a regular on BBC Radio 4's "Thought for the Day" slot on the Today programme, had arrived at the embassy in Grosvenor Place at 7pm. He said he drank "a glass or two" of Portuguese red being proffered by the eastern European servers. He was not, he insists, drunk.
Whatever the quantity imbibed, fellow guests formed the impression that by the time he left at about 9pm, he was feeling the effects of the occasion.
Patrick Cockburn, The Independent's Iraq specialist and one those attending the bash, described how the clergyman gripped him by the shoulder and repeatedly asked him for the solution to the conflict. Such was the fervour of the questioning, Mr Cockburn feared that "if I detached myself too abruptly the bishop might topple forward".
What is certain is that by the time he reached home, Dr Butler was dealing with a nasty head wound, a missing mobile phone and calls for his resignation over a number of unanswered questions, not least an apparent late-night encounter with the back seat of a stranger's Mercedes and an unspecified number of cuddly toys belonging to the owner's 11-month-old son.
When he arrived at his official residence facing Tooting Common in south London, Dr Butler found himself with a bump and cuts to the back of his head and a black eye. His briefcase and items including a crucifix and phone had vanished.
The next day he told the congregation at the induction of a vicar in nearby Dulwich that he had apparently been mugged and was unable to wear his mitre because of the swelling caused by his injuries. Otherwise, details of what happened between leaving and arriving at his home were, he said, a blank.
Fortunately for media organisations, and much to Dr Butler's increasing bemusement, others have stepped forward to fill in the gaps.
Paul Sumpter, a businessman from Beckenham in Kent, described how at 9.30pm on the night of the party he was disturbed from his game of pool in a bar by the sound of the alarm on his Mercedes parked on the aptly named Crucifix Lane, close to Dr Butler's diocesan base at Southwark Cathedral.
He said: "I rushed outside and found the doors of my car open and the man who seemed drunk with his legs hanging out of the back, chucking my son's toys about. He staggered about, fell over and hit his head against the side of pub. He then fell on the pavement and knocked himself out cold. When he came to, we offered to call him an ambulance.
"My mate was talking to him and first of all he said he was the Bishop of Woolwich. We said he looked like he had been drinking and he said, 'I am the Bishop of Southwark, this is what I do.' Then he got up and shot off." Mr Sumpter said three days later his wife found the bishop's briefcase in the car - a development that led to the couple being questioned by police for four hours and a forensic examination of the Mercedes. It was claimed the case contained Ministry of Defence papers, letters from the Archbishop of Canterbury and a Ruth Rendell novel, End in Tears.
The Metropolitan Police say they are not now treating Dr Butler's mishap as a suspected mugging, but as missing property.
Yesterday, the bishop broke his silence on the riddle of the events to say he is suffering from amnesia and undergoing medical tests, amid suggestions he may have suffered a minor stroke.
On the Today programme, Dr Butler said he had still not recovered any memory since the early stages of the party.
"It is very worrying. I still have amnesia," he said. "I am having extensive medical tests. They are still going on. I remember nothing from the time of leaving the party until I got back to my home. I am just hoping there are no long-term ill effects." He said police had traced his journey home using his Oyster card. After leaving the embassy, he walked to Green Park Tube station, took the Jubilee line to London Bridge, then the Northern Line to Tooting Bec before boarding a bus to his Streatham home. It was not immediately clear why he did not take the more direct route of walking to Victoria station and taking an overground train to Streatham.
Under questioning from John Humphrys, Dr Butler strenuously denied that he was the worse for wear. He said: "I have been going to receptions for 20 years as a bishop. It was entirely out of character if I was drunk. There are strange elements to this story. I really do defy anyone who's had too much to drink to make that journey.
"I am very careful at such receptions. Normally I have a glass or two of wine and I enjoy talking to people. I don't get drunk frequently. I wouldn't be able to do my job if I did."
Staff at the embassymaintained a studious silence last night about events at the party. A source said: "We don't want to add to any more publicity."
But Dr Butler, who has dismissed claims that his ill fortune is a resigning matter, will not be relishing a period in the spotlight which saw him pilloried on the BBC's Have I Got News for You by the Newsnight presenter Emily Maitlis, a guest at the party.
Dr Butler was appointed to Southwark in 1998, a job he was awarded ahead of a little-known Welsh bishop, Rowan Williams. Although seen as doctrinally orthodox, the bishop, who is married with two children, has not been afraid of adopting forthright positions on issues from approving gay marriages for homosexual clergy.
He is popular and has received support from parishioners and clergy. He writes a column for the local newspaper, which is called "Mitre kind of town".
Despite calls for his resignation from some clergy who have accused him of hypocrisy in his attitude towards drinking to excess, it seems unlikely that Dr Butler will have to pay for his night out with his job.
Aides said doctors were investigating whether a brain bleed caused by a small clot could have caused erratic actions. A senior clergyman said: "We are thinking it is possible that Tom had a minor stroke. That would explain his behaviour."
Certainly, the bishop was not prepared yesterday to accept his part in the strangest aspect of the saga, describing the story of his alleged discovery in the Mercedes as "very strange" and questioning whether he could have broken into it. He said his briefcase had been returned to him not by police but by a news agency and national newspaper.
Raising the fact that his phone has yet to be recovered, he added: "My injuries are still compatible with my mobile having been stolen. I certainly don't think it is a resigning matter. All I know is I arrived home with extensive wounds."
Mr Sumpter says he is the victim of false suspicions, while critics of Dr Butler have quoted at him St Paul's Epistle to Timothy: "A bishop then must be blameless... of good behaviour, given to hospitality, apt to teach; not given to wine."
As Dr Butler returned to his "Thought for the Day" slot yesterday with a homily on the plight of Bethlehem, some may have seen a retort in his decision to quote Shakespeare's The Merchant of Venice. He said: "The quality of mercy is not strained. It droppeth as the gentle rain from heaven/Upon the place beneath: it is twice blessed/It blesseth him that gives him and him that takes."