If you're French you are better off in London

He's now desperately trying to get re-elected, but back in 2007 he was still styling himself as a Gallic Margaret Thatcher ready to transform France.

At the time, the conservative firebrand launched his presidential campaign in front of an audience of London-based expats, pledging lower taxes and the kind of can-do society which his compatriots were profiting from in the UK.

"France is still your country even if you're disappointed by it," he said, pointing out that the average age of the 300,000 highly educated French nationals in Britain was 29, with a sizeable number working in the City. Many considered France an ailing backwater where strict regulation and the 35-hour week made business impossible. That's why all the big French companies made their money abroad, leaving their beautiful but increasingly anachronistic homeland to the tourists.

Plus ça change. Sarkozy's term is coming to an end yet the Eurostar remains packed with France's brightest, clutching one-way tickets. All that huffing and puffing by the little man has come to nothing, with Paris in particular remaining an overpriced, stagnating testament to its antipathy towards liberal economics. Small businesses shut down by the day, while the cost of living and unemployment rocket.

Now France's London diaspora is set to multiply, as both major French parties fight the presidential election with further attacks on "Anglo-Saxon" capitalism. Incredible as it sounds, Sarkozy sees the key to his slim hopes of re-election as raising VAT and introducing a transactions tax on share dealing in France.

Meanwhile, he has started trying to project a more caring image, arranging awkward photo opportunities with low-paid immigrant workers and the homeless, rather than with millionaire backers.

Yet François Hollande, the favourite to become France's first Socialist president for 17 years, is even more ruthless in his antipathy towards financiers. Hollande's main election pledge is, inevitably, higher taxes, especially for anyone earning the equivalent of £125,000 or more. He would also want his own presidential salary to be cut by a third, contrasting himself with Sarkozy, who raised his by 140 per cent when he won in 2007.

Hollande also wants to see a massive increase in the number of public sector workers, including 60,000 in education, and the retirement age reduced from 62 to 60. He would provide better traning opportunities for young people, especially those from disadvantaged backgrounds. This is all very commendable but what of the wealth creators needed to pay for all this, and to compete with rivals within the global economy?

Where are the increasingly ambitious, self-starting and mobile young French going to try to make their fortunes? Mayor Boris Johnson thinks he has the answer, saying last month: "Bienvenue à Londres. This is the global capital of finance. It's on your doorstep, and if your own president does not want the jobs, the opportunities and the economic growth that you generate, we do."

Whether France has a Socialist or a conservative President, Johnson's invitation looks set to be irresistible.