This week it was different.
This week the mood in the House was much more serious and sombre than it usually is at noon on Wednesdays. Occasionally a Tory MP stood up to offer mockery of the prime minister, but he was met with vocal irritation by the Labour benches and conspicuous silence from his own colleagues.
There was a feeling of genuine constitutional importance permeating the house today.
MPs know that tonight's vote is one of the moments that could end up being studied in history books, and you could feel it.
David Cameron adopted a reasoned and rational approach to the subject. There were no jokes. Instead, there were arguments - real, intellectual arguments - and debate. It was a superior moment for Mr Cameron, who appeared as prime ministerial as he ever has. He cut a serious and determined figure, and exhibited several signs of an increasing political maturity.
Many commentators view the Tories' 'principled' opposition to the 42-day detention plans as political trickery. They look at David Davis, an ex-military man and not one known for his libertarian tendencies, and question the Conservative's honesty. It was a point Gordon Brown brought up, saying: "I say in sorrow rather than anger, it is no use opposition for opposition sake."
But Mr Cameron knows he is not on the side of public opinion, and he used that unfortunate fact to surprisingly good effect - taking the upper ground and casting himself as an elder statesman of sorts.
Once Mr Brown tried to highlight inconsistencies in the Tory stance by reading from the party members' website, Mr Cameron responded: "I think that last bit is so below the level of debate."
He continued: "It is popular to bang up terrorist suspects for longer. But we're meant to do what is right in this house."
Nick Clegg stood up for the Liberal Democrats and homed in on the same point as Mr Cameron - how would the Commons be able to scrutinise the detention when discussing it would revealed confidential security information and prejudice a future trial - if, of course, there was one.
Both questions earned no real response, forcing Michael Howard - former Tory leader and the man who defeated Tony Blair on the same issue not so long ago - to stand up and ask it again.
"I want to give the prime minister the opportunity to answer a question he's conspicuously refused to answer," Mr Howard said.
Gordon Brown slipped in a little 'punch-and-judy' by pointing to Mr Howard's infamous 'did you threaten to overrule him' interview with Jeremy Paxman, saying the honourable gentleman knows a thing or two about not answering the question. Some Labour MPs enjoyed it, but he had misjudged the mood of the House. Even those who believe in extending the detention time do so, one can only presume, with a heavy heart. Many of those who vote for it are voting against their conscience and for party unity. This was not a day for jokes and mockery.
However the vote goes tonight, PMQs represented British democracy well. Never a great forum for debate and well understood by parliamentarians as the theatre it is, today it became a forum for a clash of ideas.
"The terrorists want to destroy our freedom and when we trash our liberties we do the job for them," Mr Cameron argued.
Mr Brown stressed the "first duty of the government is to protect" and defend national security.
There may be questions about why each side chose the position it chose, but whichever side of the debate you fall on: This is not the usual PMQ knockabout. It's a battle of principles.