Anthony Hilton: Osborne has also scored an own goal with his tycoon tax

In the US last year, 69 billionaires promised to give away at least half their fortunes in a scheme run by Bill Gates and Warren Buffett.

A similar scheme in the Square Mile has been set up by Lord Myners, the former City fund manager and Labour minister which more modestly seeks to get a pledge that its wealthy will leave 10 per cent of their estates to charity.

But conversation in the City was that even these sums are under pressure because of George Osborne's plans for a tycoon tax announced in the recent Budget.

Charitable donations attract tax relief, but the Budget capped the maximum amount an individual can claim in any one year at a level which means many of these seriously large donations might in future have to come out of tax-paid income.

An investment banker who raises money for his former Oxford college said at lunch on Tuesday that this is causing near-panic in fund-raising circles. Several millionaires who were on the point of making serious gifts to universities have apparently intimated they want to put their plans on hold until they see the wording of the actual legislation.

It looks like a massive own goal from Mr Osborne, considering how often the Government has stressed the need for charitable giving to fill holes left by cuts in state funding.

You could argue that the loss of tax relief should not matter to the rich because they can afford it.

That fails to appreciate their psychology. While the main satisfaction from gifting an endowment comes from the knowledge the money is going to a good cause, a secondary driver is the opportunity to put one over on the taxman.