Dan Neidle, the founder of the think tank Tax Policy Associates, told the BBC's Today programme that the £330m in tax revenue the UK could lose was "quite a lot of money".

"It is enough to fund 4,500 teachers... we have entire taxes that raise less than £330m."

"He will probably pay almost nothing in Greece, and we can't compete with that," he added.

Despite the potential loss, Neidle said there are "no easy answers and no good statistics" on the issue of ultra-wealthy taxpayers leaving the UK.

He said the Treasury has some estimates on the number of wealthy people leaving, but otherwise there are few facts about the true scale of the revenue loss.

"We have lots of anecdotes... what we don't really have is data," he said.

He said the government needed to "give certainty" to ultra-wealthy people living in the UK, arguing that lots of changes to the non-dom regime in a short space of time and reports of a possible wealth tax don't help.

"Stop rumours, stop tinkering," he said.

Rokos's decision comes ahead of UK Chancellor John Healey's first Budget on 28 October.

In an interview with the BBC on Monday, Healey did not rule out tax increases in the Budget, with a recent increase in government borrowing costs piling pressure on the public finances.

He refused to comment on any decisions about tax, promising only to "balance the books" and "control public spending".

In March, Cambridge University said the money from Rokos would be "the largest single donation made to a British university in modern times".

It will be used to create a school of government in Cambridge named after him with the aim of training leaders of the future. It is set to open this autumn.

Despite his generosity to Cambridge, Rokos is an Oxford graduate, having studied mathematics at Pembroke College.

He attended a state primary school before winning a scholarship to Eton College.