Gordon Brown and Nicolas Sarkozy both need to make a success of the state visit. With Labour's poll ratings low, and trouble in the economy, it may help Mr Brown to be seen walking the world stage. M. Sarkozy has also seen his domestic poll ratings in free fall because of the economy – and his private life – but some of the issues he wants to bring to the negotiating table may only add to Mr Brown's troubles on the home front.
France will take over the Presidency of the EU on 1 July, and M. Sarkozy was to use his six months in Europe's driving seat to push through implementation of the Lisbon Treaty, a sore point in the UK. He wants to have a permanent EU president and an EU foreign minister in place by the end of the year.
Most ambitiously of all, he wants to bring France back into Nato, abandoned more than 40 years ago by General de Gaulle, a development other Nato members would welcome but in return, M. Sarkozy wants an agreement to create a "common intervention force" made up of 10,000 troops from each of the six biggest EU states, including Britain, as a step towards creating an integrated EU army.
Today and tomorrow will be an ordeal for Sarah Brown, who has not played the role of Prime Minister's wife at an occasion this formal before. She will be at her husband's side when the French party arrives at the Commons this afternoon and again on the steps of 10 Downing Street tomorrow morning before the serious politics begins.
She will have to look after Mme Sarkozy for the next four hours, while the Prime Minister and the President visit the Emirates Stadium. That will include giving a brief talk before lunch at Lancaster House on the subject of maternal mortality.
But at least Mrs Brown, who is not a great lover of publicity, will have the comfort of knowing that she is not the one attracting the eyes of the curious. The French President's wife, the 40-year-old Carla Bruni, is possibly the most colourful character to arrive in Britain on a state visit. She is actually more accustomed to meeting the rich and famous than her husband, having been born among them. She is the daughter of an Italian industrialist and an opera singer, and she has stepped out with at least one knight of the realm – Sir Mick Jagger, with whom she toured many years ago. Contrary to rumour, the former model turned singer is not going to strum her guitar in one of the state rooms in Windsor Castle, but in France her record company is insouciantly using the state visit to promote herlatest CD.
When the visit was first planned, it was thought that palace officials might insist on the President and his new love sleeping in separate rooms, for although their affair was public, they were not yet married. The wedding took place quietly last month.
What a relief.
For the Queen, the most important concern is that tonight's state banquet at Windsor, the 96th in her reign, should pass off perfectly. It will be held in St George's Hall, a panelled room 185ft long and 30ft wide, on a mahogany table that seats 160. When assembled, the table is the largest piece of furniture in Britain. Place settings have to be exactly 17 inches apart. The palace has not said what is on the menu, prepared by the chef Mark Flanagan, because the Queen likes to check it personally on the day. She also takes a minute interest in the seating arrangements. The guests, including Gordon Brown, the French celebrity chef Michel Roux and the BBC's Andrew Marr, must wait in the nearby Waterloo Chamber while the Royal Family and the French President and his wife assemble in the Oak Room, and then proceed to the Grand Reception Room, where guests file past to be introduced before taking their seats. When they are seated, the Irish Guards will pipe in the royal procession, led by the Queen and the President. Before food is served, the Queen will propose a toast and M. Sarkozy will respond.
With so much serious business to discuss, you would think Mr Brown and M. Sarkozy would want to shut themselves away somewhere quiet for several hours. In fact, they will spend about 40 minutes in the Prime Minister's Downing Street office before setting off for the Emirates Stadium, which is sometimes called the other French embassy.
They will be met by Arsenal's French manager, Arsène Wenger, who will lead them on to the pitch to meet members of the local community football school. According to Mr Brown's spokesman, "the Prime Minister is unlikely to kick a ball". They will, however, give a joint press conference in the Royal Oak Room at the club.
Because it is a state visit, the Sarkozys are officially guests of the Queen, not Gordon Brown. As they disembark from their aircraft to the red carpet on the tarmac at Heathrow, the first people they will see will be Prince Charles and Camilla, whose job will be to escort them to Windsor.
The Queen will be waiting on a special dais in Datchet Road, Windsor to welcome the French party formally to the United Kingdom. Other officials waiting with her will include a few with ancient titles such as the High Sheriff of Berkshire, and the Silver Stick in Waiting.
The Queen and the French President will then climb aboard a state carriage to lead the procession to Windsor Castle. Prince Philip and Mme Sarkozy will follow in the second carriage, Charles and Camilla in the third.
They will all have lunch in the state dining room, a smaller room than the one where the state banquet will be held, but still large by most people's standards – 40ft long, and 30ft wide, with three windows overlooking the Thames.
After lunch, they will walk through to the White Drawing Room, which adjoins the Queen's private apartments, to see an exhibition of French items from the Royal Collection, including a drawing of Napoleon II by Queen Victoria. This evening, the Sarkozys will sleep in magnificent rooms on the south side of the castle. In the morning, they will awake to a breathtaking view of Windsor Great Park and its famous Long Walk.
Mme Sarkozy will not be the only member of the President's entourage adding glamour to the visit. The party staying overnight at Windsor Castle will include France's Secretary of State for Justice, Rachida Dati. The second of 12 children of poor immigrants, she is France's highest ranking person of north African descent. President Sarkozy has called her, with typical disregard for political correctness, "my little Arab girl".
She enraged judges and lawyers in France last year by posing for glamour shots in Paris Match magazine at about the same time that she inflicted drastic economies on the court system.
At other times, her knee-high boots and fishnet stockings have caused comment.
She will be vying for attention with Rama Yade (above), France's 32-year-old deputy foreign minister in charge of human rights, who was born in Senegal and is married to a Yiddish socialist singer.
She is said to have locked her husband in at home to stop him voting for the left in the presidential election.
Expect the tabloid press to run pictures of the two strikingly good-looking ministers, alongside unflattering photographs of their British equivalents, such as Harriet Harman.
The French President's formidable mother, Andrée Sarkozy, was expected to join her son on the visit but cancelled at short notice for personal reasons. His mother-in-law, Madame Marisa Borini-Tedeschi, will be there.
The French couple will not have a lot of time for sightseeing, but they will call at Carlton Gardens tomorrow morning to lay a wreath and observe a minute's silence at the statue of General Charles de Gaulle. In the afternoon, they will travel downstream on the Thames clipper Aurora to Greenwich to visit the Royal Observatory and the Old Royal Naval College, a personal request by M. Sarkozy. In France, they call him the "bling-bling" President because of his fondness for Rolex watches, so it seems appropriate that he should want to visit the point from which time is measured around the world.