First Brown ... now Darling - the stress gets to Downing Street

The former Chancellor – during his resignation speech in the Commons on November 13, 1990 – claimed being in Margaret Thatcher’s Cabinet was like discovering you were the opening batsman – only to find your cricket bat had been ‘broken by the team captain’.

Just as Sir Geoffrey could no longer take Mrs Thatcher’s lectures, it seems Mr Darling has finally rebelled against domineering Mr Brown.

Rebels: Alistair Darling seems to be following in the footsteps of Geoffrey Howe

The pair have spent much of the past ten years telling voters that the days of boom and bust are over, ruling the country with no opposition from a broken Tory Party.

Not any more. The boom is over, the country is going bust and David Cameron is 20 points ahead in the opinion polls.

Nor is Mr Darling the only one to be showing signs of strain. When I interviewed Mr Brown in Beijing last week, he behaved in a way I can describe only as unusual.

After discussing Britain’s success at the Games, I asked him some routine questions about his problems back at home, the sort of thing a novice MP would field without blinking.

His mood blackened the moment I mentioned his speech to next month’s Labour conference. He grunted: ‘Everything is important. Every speech is important.’

When I pursued the matter, he snapped: ‘I will be pleased to talk about the conference at the time of the conference. Till then, I will be getting on with dealing with the economy.’

Snappish: Gordon Brown

To be fair to Mr Brown, he may have thought the interview was going to be restricted to Team GB’s Olympic triumphs, not his domestic woes.

But as a politician with more than 35 years’ experience, he must have realised that even when a Prime Minister is abroad at a sporting event, any reporter worth his salt is going to ask about the main political issues back home.

He grimaced at the mere mention of David Miliband’s name and declined to answer.

More than once, Mr Brown half rose from his chair as if to indicate the interview was over. I stayed put and he backed down.

At other times, he glared at his No10 adviser as if to say ‘get me out of here’.

He told me: ‘I have given you special time. That is very good of me.’ He laughed loudly, saying I was ‘fortunate’ to get the chance to speak to him at all.

Later, I described our meeting to a senior Labour figure, who replied with a look of resignation: ‘Welcome to our world.’

It should be pointed out that Mr Brown had been put through the wringer in a series of earlier TV interviews about his hopes of survival.

Clearly, Mr Brown had to keep his composure on TV, unlike an interview with a newspaper reporter, where his body language was not being filmed.

Certainly, his mood was transformed when we spoke again on the way back to London, chatting amiably about how Britain could do even better at the 2012 Games.

Back in 1990, Sir Geoffrey’s devastating remarks triggered a leadership challenge within 24 hours. Two weeks later, Mrs Thatcher was forced to resign.

No one expects events to move as fast after Mr Darling’s outburst. For a start he hasn’t resigned – yet. But he has made it more likely that Mr Brown will go sooner rather than later.