It must take superhuman self-control for MPs to refrain from yelling things at Tony Blair when he calls on them to answer him during question time.
By Nick Assinder
BBC News Online Political Correspondent
No surprise then that many MPs simply can't manage it and end up virtually screaming at him in (thanks to the microphone system) near-silent frustration.
Kennedy jumped into education spat
The experienced, however, know when to keep quiet and remain absolutely passive.
As Don Corleone might say: "Never let people know what you are thinking".
And, in this bear pit, even blinks and involuntary twitches can be read by your opponents as laden with a meaning completely unintended by the twitcher.
Needless to say, it really is not the done thing for the prime minister to ask his opponents questions when they are sitting down and don't have the automatic right to answer.
Obviously then, it can and regularly is used to good effect, particularly at the end of a spat when the prime minister's opponent has run out of his allotted number of questions.
They all have their own ways of dealing with it.
Kennedy needs a poker face
Michael Howard crosses his arms over his chest, grips his lapels and sometimes pokes the air at the prime minister while muttering what we are all supposed to read as comprehensive put downs.
Or he adopts the more traditional approach of simply sitting there shaking his head in theatrical disbelief at the prime minister's apparent ludicrousness.
Charles Kennedy is still perfecting his approach - and he is getting plenty of practice at the moment.
For some reason Mr Blair takes particular pleasure in using this trick with the Liberal Democrat leader. And he was at it again this week.
After another lengthy session with Mr Blair and Mr Howard challenging each other's policies on education and whose choice was bigger than the other's, Mr Kennedy jumped in.
Howard grips his lapels
When was Labour going to stop trying to out-bid the Tories over selection, he wanted to know.
All the public want is good quality state schools in their locality, he said, with what many might believe was utmost reasonableness.
Not the prime minister, who went on to challenge him time and again on his own policies.
Well, the prime minister asked, does he support our city academies? Does he support our specialist schools?
All routine stuff. But instead of presenting a poker face, the Lib Dem leader blinked. Fatal.
Aha! - then perhaps he should cross the floor and join us, joked the prime minister.
"He would never make it", joined in a Labour backbencher.
By the way, Labour is facing two by-elections next week where the Liberal Democrats hope to do rather well at Labour's expense.