Rain spits down on the garden of the Oxford Union. The lawn that 48 hours earlier hosted a Rio Carnival Ball with salsa dancers, fire-eaters and Brazilian cocktails turns quickly to sticky mud.
A few feet away, inside the historic debating chamber, a teenage Welsh chanteuse is standing on the rostrum and painting a very different picture.
"Summer-time," belts out Charlotte Church, to an audience of 600 of Britain's finest young minds, "And the living is easy, fish are jumpin' and the cotton is high."
Life is indeed pretty good for the members of Oxford University's most famous private club, who pay their £165 life membership fee for the right to hear and argue with some of the most high-profile, powerful and controversial figures of our times and to drink in the only bar in the city that still sells beer at £1 a pint.
Ms Church is not giving a concert. She is, at 17, the young-est guest speaker to address the Union. One wonders what her appearance would have done for Gladstone, Macmillan and Asquith, three former presidents whose busts line the chamber walls. After arriving at the Union, the singer is whisked away to the Randolph Hotel for dinner with the club's top brass, and returned in time to pose with Walker for pictures in front of the bookcases of the library.
When the singer steps up to speak, she is introduced by Marcus Walker, Union president, as "the lady with the voice of an angel". The "Termcard" - the Union's programme of events - describes her less reverentially as "the Welsh chorister, who won the much coveted Rear of the Year at the tender age of 16". Some male students refer to her as "hot". As she begins her address, Ms Church tells the students she is "not here to whinge" and then spends 90 minutes complaining of headlines such as "Hell's Angel: Rebel Charlotte in Biker T Shirt".
If the Oxford Union was to face an accusation of dumbing down it would not be the first time. The ubiquitous Chris Eubank is another of this term's guests and last year the hypnotist Paul McKenna persuaded students to put their trousers on back to front.
No president is likely to ever out-dumb the incumbent who booked Kermit the Frog, star of The Muppet Show, to address the famous chamber, although previous luminaries who have stood inside the debating chamber have included Barry White, Gail Porter, Jon Bon Jovi, O J Simpson and David Ginola. Michael Jackson's appearance, with a vast entourage including Uri Geller and Rabbi Shmuley Boteach, provoked a paparazzi frenzy.
Given this, it is surprising, and more interesting, that this Michaelmas term the programme of debates has included political heavyweights such as Madeleine Albright, Lord Heseltine, Michael Ancram and Hollywood stars such as Clint Eastwood and Christopher Lee. And they all perform free. When the Union puts on its first carol service next month a government minister, Paul Boateng, will preach to the congregation.
This is the organisation that justly bills itself as "the world's largest and most famous debating society" on its slick website. Founded in 1823, the Oxford Union now costs a staggering £700,000 a year to run. About £500,000 of this is understood to come from new membership fees from the bulk of the 5,000 students who join Oxford each year.
Cambridge runs a similar operation, with guests this year ranging from Vanessa-Mae to Carole Caplin; but it is on a smaller scale. Oxford thinks big.
The Oxford Union began as a small club for students in the early 19th century who were frustrated at the university's restrictions on political debate. It has grown to become an enterprise that its founders could never have imagined.
As president, Mr Walker, 22, studying Byzantine history at Oriel College, relies on support from a librarian, a treasurer, a secretary and five members of a standing committee who are all students elected from within the Union's membership.
He also has a team of six salaried employees ranging from a bursar to a steward. The latter, Salvatore Salamone, is described by Mr Walker as "a big fat Sicilian, he looks like he should be a Mafia don" and is tonight maintaining security among the students that have assembled to hear Ms Church. Mr Salamone is also due to appear as Santa Claus at the Union's Christmas Party.
The high level of media interest in the organisation (not least from Cherwell and The Oxford Student, the University's weekly student papers and Isis, a monthly magazine) means it needs its own press officer, Paulius Kuncinas, 25, who is doing an MPhil in Russian and Eastern European studies and comes from Vilnius in Lithuania.
The Union has an unofficial chaplain, the Reverend David Johnson, who is described in the Termcard as "Champion debater; 'Vicar'. Mad." The Reverend caused some controversy earlier this year when he described Clint Eastwood as a "ludicrous man" to a reporter from The Independent. On this occasion, The Independent promises Mr Kuncinas not to publish the chaplain's comments regarding Ms Church.
Being president of the Oxford Union is perhaps the most coveted student position at the University, a role previously held by such luminaries as Lord Salisbury, Benazir Bhutto, Michael Heseltine and William Hague.
The most famous of the recent presidents is Boris Johnson, the Conservative MP for Henley and editor of The Spectator magazine. According to Mr Kuncinas nearly all the recent incumbents have "gone into investment banks".
The Union, which estimates that between 60 and 65 per cent of Oxford students are members, describes itself as "the centre of Oxford life", acting as a social mecca for the university's 39 colleges, which otherwise operate as self- contained entities.
It is not to be confused with the Oxford University Student Union (free and automatic membership), which campaigns for student rights and organises protest marches in the wide world beyond the shadows of the dreaming spires. That organisation is, one could fairly say, a lot less glamorous than the Union.
Being president of OUSU (a position recently held by William Straw, son of Jack, the Foreign Secretary) offers a salary of £10,500 to the winner of a keenly contested annual electoral campaign. Presidents of the Union, by contrast, hold their post for just a term, during which they are obliged to support themselves.
As he relaxes in the Union bar, Mr Walker is clearly enjoying his stint in the president's chair. The son of the Times journalist Christopher Walker, he also held the presidency of the Oxford University Conservative Association. "Not wanting to brag but I'm the first person since [William] Hague to do the double," he points out.
His popularity is such that he has managed to draw support from different shades of Oxford student politics and is named by Isis as one of its five university "Icons". The magazine describes him as "Byzantine historian, headline grabber and lovable 'loon'".
OU presidents are supposed to be elected for being nothing more than a good chap or chapess and any form of campaigning is expressly forbidden. Inevitably, this leads to lots of meetings held in secret. "Officially you are not allowed to campaign, you are not allowed to have a slate. You are not allowed to mention the election. There is every rule under the sun," Mr Walker says knowingly. "I did what every candidate does to win the election."
Furthermore, serving officials of the Union are invariably competing with one another for the president's chair, Walker complains: "Half the people on my standing committee are running against the other half and are perfectly happy to leak stuff to the press that will damage the other side and also damage the Union. You have to ensure that you are reining both sides in at all times."
He acknowledges that being president of the Oxford Union sits well on a CV but says he has yet to decide what career to take. He has ruled out the City but is intrigued by journalism and may yet go into politics "many years down the line".
Walker gets the chance not only to pick his guests but to hobnob with them and have his picture taken. It is no surprise that his list is packed with Tory grandees including Douglas Hurd, Chris Patten and Michael Heseltine ("sizzling") as well as the former mayor of Carmel, California, Clint Eastwood ("brilliant").
Mr Walker, who has introduced a cut-price membership fee of £105 for students from low-income families, spent the whole summer vacation arranging his itinerary of speakers and debates. The Union may have a track record that includes Mother Teresa of Calcutta, the Dalai Lama and Presidents Nixon, Reagan and Carter, but it is competing against the rest of the global media (and huge budgets) for access to big names.
The president has chosen eight subjects of debate including "This House believes that the British Empire was one of the greatest forces for good the world has ever seen" (speakers including the former Daily Telegraph editor Lord Deedes) and the Iraq- related motion "This House believes that we are losing the Peace", which featured the veteran Labour MP Tam Dalyell and had students queuing round the building.
The Union has been cute to the idea that sponsorship of debates has value to potential employers of those in the audience and City institutions - NatWest, JP Morgan, Lehman Brothers - have rushed to have their names associated with events. Mr Walker admits that "without sponsorship money coming in we wouldn't be able to survive".
The president and his team must also, with their £700,000, finance the upkeep of grade II-listed buildings that include the Old Library, decorated with the murals of William Morris and the Alfred Waterhouse- designed debating chamber, surrounded on all sides with wooden galleries from which students crane to hear the illustrious speakers.
The Union's financial acumen extends to making some of its beautiful rooms available for hire, although a disastrous project to convert one of them, the Macmillan room, into a pasta restaurant resulted in losses of £40,000.
Mr Walker personally selected his list of guest speakers (which also included the farmer Tony Martin, the rap star Wyclef Jean, Germaine Greer and Clare Short). Tony Blair rejected his overtures despite having taken a swipe at the Union in a magazine interview.
Walker defends the selection of Charlotte Church on the basis that "I think she will be fascinating to hear for the members. I have tried to have a wide range of speakers to appeal to all the different interests of the student spectrum."
As well as the Rio Carnival, this term offers a Barbados Day (rum punch), Trafalgar Day Celebrations (tot of Navy rum), Christmas Party (mulled wine), and a paintball contest against the rival and lesser-known Cambridge Union, whose members are referred to as "Tabs" (short for Cantabrians).
The Cambridge Union was in fact a model for the Oxford society, being founded eight years earlier in 1815 and also housed in a Waterhouse-designed Grade II listed building.
It has been addressed by Lloyd George, Roosevelt and Nehru. John Maynard Keynes was president in the 1930s and Union officers have included Kenneth Clarke, Michael Howard and David Frost. But as Walker said: "They have yet to produce a Prime Minister, which does not bode well for Mr Howard."
Other universities may offer the latest in indie rock groups, toga parties and stand-up comedians but there is nothing quite like the Oxford Union.
The Union must accommodate the competitive student debaters, who battle for trophies such as the Richard O'Sullivan Memorial Debater of the Year and the Moynihan Plate College Pairs.
Freshers are offered workshops in debating skills. Its website describes debating as the organisation's "lifeblood" and its "raison d'etre". But Walker, who sees the Union primarily as a social centre, does not concur. "There are many other facets which people seem to enjoy," he says.
Monday evening ends with Ms Church making a plea for legislation against media intrusion into the lives of under-18s while she also entertains students with a slide show of some of her more lurid press headlines.
The chorister is asked from the floor if she'd rather give up singing or sex. She cannot answer but gets a laugh anyway. Her mixture of warbling and whining has gone down a storm and she is heartily applauded out of the room.
"We don't get bands, it's more cerebral," says Chris Hallebro, 21, studying English and history at St Peter's. "It's what university is all about. It's expanding your horizons."