Gordon Brown should enjoy his moment on the global stage. He has undoubtedly had a diplomatic success in chairing the G20 summit; however, it is unlikely to last.

Like many previous prime ministers, he will soon discover the harsh contrast between the glow of international summitry and the brutal realities of domestic politics. Voters are an unforgiving lot. They like to see their leaders being taken seriously, but there is no evidence that past summits have made any real difference domestically.

Mr Brown may see an immediate boost to his poll ratings after all the publicity, photo opportunities and even praise this week, but I doubt if it will last beyond Easter.

That is not to question either Mr Brown’s commitment and energy over the past few weeks or the substance of the pledges in yesterday’s communiqué. The Prime Minister presented the outcome in terms of jobs saved and created. The problem is the gap between yesterday’s promises and good intentions, and what happens on the ground. As George Osborne said in the Commons, will small businesses feel more secure, mothers working on the high street less fearful about their jobs or families less worried about their homes?

The key, as Alistair Darling argued in his statement to MPs, is implementation. There will still be time lags before activity recovers and unemployment stops rising. Things are going to get worse.

For most British voters, the Budget in just under three weeks’ time on April 22 will be far more important. Mr Brown can fairly claim endorsement from other leaders for his Government’s fiscal stimulus so far, but as Mervyn King, the Governor of the Bank of England, pointed out last week, there is not scope within already very high borrowing levels for a further general stimulus, as opposed to measures targeted on particular groups. We will no doubt see action to safeguard the jobs of those already working part-time (probably through tax credits) and to help savers.

Within two months the European and English county elections on June 4 are certain to be bad for Labour. So the G20 summit is likely to be at most a temporary fillip to Mr Brown’s standing. His and Labour’s chances of avoiding a general election defeat depend entirely on credible evidence of economic recovery — and that may not be enough. As Mr Brown said yesterday, there are no quick fixes.

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