The Big Question: As M. Sarkozy visits London, how cordial are Franco-British relations?

Why are we asking this now?

President Nicolas Sarkozy arrives in Britain for a two-day state visit tomorrow. He and Mme Carla Bruni-Sarkozy will take tea with the Queen, ride in state carriages through the streets of Windsor, and attend two official banquets. President Sarkozy and Gordon Brown, and a dozen French and British ministers, will hold the annual Franco-British summit on Thursday amid the unusual surroundings of the new Emirates football stadium in North London.

What's the state of Franco-British relations?

There has been no serious spat for nearly three years, which must be something of a record. There has been no violent dispute over foreign policy since the argument over the Iraq invasion in 2003. There has been no dispute over immigration since the closure of the Sangatte refugee camp near Calais in 2002. And there has been no row over EU farm policy, or the British rebate, since late 2005.

Instead, the two governments are co-operating placidly against illegal immigration. They are jointly developing a new type of aircraft carrier and are ready, we are told, to announce a joint venture to create a new generation of nuclear power stations. How specific this agreement will be (co-operation has been going on for years) remains to be seen.

And relations between the two peoples?

Ah, that depends who you listen to. The British press still loves to bash or tease the French. The French media, especially French television, likes nothing better than to run a story about the eccentric Anglais (rarely the Scots or Welsh). The image persists in France that we are a nation evenly divided between punk rockers and men in bowler hats carrying rolled-up umbrellas.

In truth, something odd has been happening in French-British relations for quite a while. The two countries have been quietly merging. There are 300,000, mostly young, French people living in Britain (mostly in London). There are 250,000 British people living in France, mostly middle-aged, retired and living in rural areas. Some of Britain's greatest, recent folk heroes have been French, from Eric Cantona to Thierry Henry. One of Britain's greatest actresses, Kristen Scott-Thomas, who lives in Paris, said last week that she now regarded herself as a "Frenchwoman who spent her childhood in England".

Do Gordon and Nicolas get on?

Remarkably well. At the EU summit in Brussels earlier this month, they disappeared for a private, very friendly chat while the President of the European Parliament, Hans-Gert Pottering, addressed (interminably) the other leaders. The two men first met when they were both finance ministers in 2004. They might appear to be Scots chalk and French fromage, Gordon dour and ponderous, Nicolas, all glitter and hyperactivity. But for some reason, the chemistry between them works.

A word of warning, however. Jacques Chirac and Tony Blair were also, briefly, the best of friends. Something usually turns up to sour relations between the Elysee and No.10. In a host of areas, from trade policy to the future of the EU farm policy and the British "rebate", the Sarkozy-Brown entente may be a spat waiting to happen.

What's on the summit agenda?

The world financial crisis. The French presidency of the EU, in the second half of this year. Nuclear co-operation. Immigration. China and the Olympics. Afghanistan. The problem with summits of this kind is that the press demands some important breakthrough or decision. The summit communiqué generally tries to oblige, often by wrapping up in shiny paper something that has been around for years.

There is talk of a new "package" of measures to fight illegal immigration. There is talk of a French-British accord to develop a new generation of nuclear power stations and sell the technology to other countries. London and Paris are already co-operating well in these areas. It remains to be seen if Mr Brown and M. Sarkozy genuinely have anything new to say.

Do Franco-British relations matter as they once did?

Oui et non. London and Paris no longer have their one-time diplomatic or economic clout. On the other hand, British and French interests have converged, in the face of threats from globalisation, militant Islam, even the enlargement of the EU. London and Paris – even Paris and Berlin – can no longer boss 27 EU countries, in the way that they once bossed 10 or 15. On the other hand, Britain and France remain permanent members of the US security council. They remain, for good or ill, nuclear powers. They remain the only significant military powers in Europe, west of Russia. They remain the third and fourth largest economies in the world.

France is Britain's third-largest export market, taking one tenth of all our sales. We are France's fourth largest export customer. At the end of 2005, Britain was the single biggest accumulated foreign investor in France. The French are the third largest foreign investors in the UK.

How is Sarkozy doing as president?

He is in trouble, like Gordon Brown, but for very different reasons. The Prime Minister is accused of being indecisive. President Sarkozy is accused of making too many decisions, too quickly, and taking the whole burden of government onto himself. He promised "rupture" with the past. He promised to seek growth with "my teeth". He promised to make France work harder and earn more. After 10 months, France finds itself with unemployment falling rapidly (partly for demographic reasons) but also with plunging living standards for ordinary people.

President Sarkozy might have got away with it if he had not drawn attention to his own show-biz life-style and sometimes behaved in unpresidential manner (such as descending into slanging matches with strangers at farm shows). A "Sarkozy Nouveau" is promised, starting with his London state visit. His suits have become heavier, darker and boxier. His Ray-Bans and Rolexes have been banished. The ceremonial parts of President Sarkozy's visit will be far more watched in France than the politics of the "Arsenal summit" at the Emirates Stadium.

So are we entering a Franco-British golden age?

Don't count on it. The essential relationship between the two countries will remain good but three years without a brotherly, or sisterly cross-Channel spat, is extraordinary. It cannot last.

So are Brown and Sarkozy destined to enjoy a warm partnership?

Oui...

*The two men are not at alike as personalities, but they get on surprisingly well and share a background in running national finances

n British and French interests, both in the EU and the wider world, are converging

*Nicolas Sarkozy admires the 'Anglo-Saxon' liberal approach to economic policy

Non...

*French and British relations are never calm for very long, as Tony Blair and Jacques Chirac discovered

*Nicolas Sarkozy, whatever he may say, is an economic interventionist and protectionist at heart

*After flirting with an Anglo-French entente, previous French leaders have reverted to the Paris-Berlin double act