Another summit, another riot. The violence seen on the streets of London as world leaders gather for the G20 summit is as predictable as it is pointless.

Thugs who smashed windows at branches of Royal Bank of Scotland are presumably not protesting against the nationalisation of a high street bank and state interference in the free market.

They must also be vaguely aware that Sir Fred Goodwin, the former RBS boss who has become a symbol of all that is wrong with the banking sector, will not be called upon to pay for their damage.

But while attention inevitably focuses on a violent minority, London has also attracted many thousands of campaigners with rather more to say, and a better idea how to say it.

Everyone from CND to pro-Palestinian campaigners and environmentalists has converged on the capital. Millions of others will be watching intently to see whether Gordon Brown and his guests succeed in coming to an agreement on ways to fix the world’s economy.

Regulatory reform and freeing up credit are not causes that set the pulse racing or inspire snappy banners.

But these are the issues that the G20 needs to address if it is to be seen as a success. Making credit available to businesses will allow them to trade, so that they can continue making things or providing services, and continue to employ people.

Reforming the world’s banking systems will, perhaps, prevent disasters such as the credit crunch befalling the world in the future.

The third plank in Mr Brown’s economic plan, a massive fiscal stimulus, appears to have been abandoned. This is hardly surprising, as many of the nations taking part in the G20 are clearly reluctant to embark on a major programme of public spending.

But it is debatable whether more public spending is what Britain needs right now anyway.

And even leaving this issue aside, there is plenty for the G20 do to.

However, it may be a mistake to set expectations too high. The summit itself lasts for only one day, and there is no reason to think 20 nations will suddenly agree on meaningful reforms when they agree on so little else.

As recent comments by the French have made clear, any attempts to stitch up a deal in advance have failed.

Mr Brown has made big promises about the G20. We will find out today whether it lives up to the hype.