But as the whips were scurrying around Westminster on Tuesday night, assessing their chances of avoiding defeat in the terrorism vote, Labour MPs came close to fighting.

At the centre of it all was probably Labour’s (among his own side) least popular MP, Bob Marshall-Andrews. The rebellious QC, who represents Medway, has regularly voted against his Government and was one of Tony Blair’s most persistent critics over Iraq.

On election night, May 5, Mr Marshall-Andrews appeared on television to announce that he had lost. Labour figures across the country were said to have cheered, claiming that it would be a vote gained for the Government. In the event he had got it wrong and he returned to dog the whips.

Mr Marshall-Andrews was already in trouble with his colleagues after this week’s Parliamentary Labour Party meeting, in which Tony Blair took on his critics. After the meeting he came out to begin briefing journalists about what was supposed to be a private meeting. Many shouted and cursed him.

On Tuesday night he did the wrong thing again: he started talking to the enemy. He was chatting with three senior Tories — Andrew Mitchell, Damian Green and Greg Knight —in the lobby outside the Commons chamber.

Barry Sheerman, the senior Labour MP and chairman of the Commons Education Committee, happened upon the scene and attacked Mr Marshall-Andrews for talking to his “friends” in the Tory party. Mr Marshall-Andrews shouted back at him and suggested that Mr Sheerman might have taken drink.

At that point Jim Dowd, the pugnacious Labour MP for Lewisham West, arrived to begin haranguing Mr Marshall-Andrews, who insulted him and again implied that he was the worse for wear. It was too much for Mr Dowd, who grabbed his foe by the lapels and began pushing him across the lobby, finally pinning him against a wall.

Fortunately, the Labour whips’ office is in the opposite corner of the lobby and they were quickly alerted. Tom Watson, the genial and rotund junior whip, raced to the fracas and pulled Mr Dowd away from his adversary.

Other whips — known as the Westminster “thought police” — appeared swiftly to surround the combatants and defuse the situation,fearful that the real police might have to be called in.

Mr Dowd retired from the area and Mr Marshall- Andrews went back to his Conservative “friends”.

Later, with tongue slightly in cheek, Mr Mitchell described it as an “unprovoked and unpleasant attack on a distinguished senior parliamentarian. It was mercifully defused with speed and efficiency by the government whips.”

Mr Green said: “It was the first time I have seen physical violence in the lobby.”

There was one final twist. Ian Cawsey, the Labour whip, took out his mobile phone and photographed Mr Marshall-Andrews talking to the Conservatives. He had evidence to present to the party against the recalcitrant MP, and it would not take 90 days to charge him.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Olympic-size television coming to your town
• Mosley opens new front in battle for privacy
• Decorator fined for smoking in van