When the Queen’s hat is the most flamboyant item of costume in a gathering, then it is a sober affair. Yesterday, as Nicolas Sarkozy and his new wife, Carla Bruni, arrived at Windsor Castle, nothing about the staging would have flattered President Bling-Bling, the sobriquet that Mr Sarkozy is so keen to discard. Beige dress (on the Queen), grey coat (on Bruni), beige castle, grey-uniformed soldiers, grey horses, grey sky: it set the tone of seriousness that French officials have worked so hard to secure.

To that extent, Mr Sarkozy will get what he wants from this visit, with speeches in the Commons and in Guildhall and hours of meetings today with Gordon Brown and other ministers. It will relaunch him as a statesman (he hopes), and distract critics from his whirlwind courtship of Bruni, his paralysed plans for reform of the economy and his party’s defeat in local elections a few weeks ago.

Enthusiastic overtures from a French president are hardly unwelcome in Britain, even if an immediate use for them is unclear. Tony Blair and Jacques Chirac were barely on speaking terms by the end, divided by Iraq, their conviction in their nations’ opposite missions, and an excess of self-belief. Compare that with the warmth of Mr Sarkozy’s remarks yesterday morning on the BBC Radio 4 Today programme, when he called for “a new Franco-British brotherhood”.

But the problem is that what he appears to envisage goes not just beyond what Britain wants, but what he can deliver. Take his frequent hint since September that he might take France back into the military command of Nato, reversing General Charles de Gaulle’s decision of 1966. That move, which has cast a shadow over France’s relations with Britain and the US since then, arose from a dispute about putting French forces under foreign command, although it was partially reversed by Mr Chirac in the 1990s.

However, for all Mr Sarkozy’s remarks that reintegration is very likely, he has coupled that proposal with talk about closer European defence cooperation. To the extent that this means anything (he has left it vague), it will be anathema to Britain, never mind the US. To couple a tantalising proposition with an impossible one is not to promise anything at all.

For all Mr Sarkozy’s talk of common ground with Britain on the economy, his protectionist attitude about preserving national champions and defending France from sovereign wealth funds (which have not shown much interest in it) will not chime with Brown’s instincts. He will be on better ground with nuclear power, yet to turn up trumpeting vigorous cooperation on a subject which is so highly charged in Britain (unlike France), is more useful for Mr Sarkozy than for Brown.

Mr Sarkozy cannot be blamed entirely for the lack of progress of his much vaunted reforms since he was elected last May. They were always going to be hard to push through, and the recent elections showed how little appetite many voters have for the inevitable discomfort.

But almost a year of President Sarkozy has produced little of significance. Even though he has toned down the glitz on this trip, that does not mean that he can so easily add substance to his promises.

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