Their demand, on the day of the failed second bomb attack on the capital's transport system, was straightforward: they wanted sweeping powers to hold suspects without charge for up to three months. This, they said, was the minimum required to break up the complex terrorist networks which were threatening Britain's security.
Some believed that the request was merely the opening gambit in a Whitehall bidding war. But, within days, the police request had won the enthusiastic support of the Prime Minister, who relayed the message to his holidaying Home Secretary, Charles Clarke.
Today, Home Office ministers will stand up in the House of Commons to defend the idea, and a host of other highly controversial anti-terror measures intended to reach the statute book before Christmas. Ranged against them will be a phalanx of critics, including the main opposition parties and a Labour left in full revolt. Then there is the increasingly vocal coalition of lawyers, human rights groups and senior judges.
Their fears are summed up by the strongly worded submission from Amnesty International, which is better known for organising campaigns against totalitarian regimes in the developing world.
The flashpoints during today's committee stage of the Terrorism Bill, which, because of its sensitivity, unusually is being held on the floor of the Commons, will be the proposed 90-day detention without charge and plans to outlaw the "glorification" of terrorist acts.
Today's debate marks the opening skirmishes in a parliamentary battle that will dominate the Government's agenda over the autumn.
Ministers know the proposed detention plans will be savaged by the lawyers and judges in the House of Lords, and are likely to give ground before the legislation leaves the Commons.
Mr Clarke has already said that he may be flexible, talking about giving judges more power to approve detention and allowing police to question terror suspects after they have been charged with relatively minor "holding" offences.
Concessions are likely to be held back until the Bill reaches its crucial report stage and third reading next week - the point at which opposition parties and Labour rebels are planning to pounce. One possible compromise is to double the current 14-day limit on holding suspects to 28 days, although neither Tories nor Liberal Democrats have shown any willingness to enter a "Dutch auction" on the issue.
The planned offence of "glorification" of terrorism is also incendiary. The Home Office has already watered down the measure, but still faces accusations that it could criminalise anyone who advocates resistance to a brutal dictatorship. Unfortunately, many Labour MPs can remember all too well doing just that in the days of apartheid and Chile's Pinochet regime during the 1970s.
One thing is certain: rebel Labour MPs now have the numbers needed to force ministers to the negotiating table. Fifty-four Labour backbenchers who rebelled over the last anti-terrorism legislation in March are still in the Commons. If - and it is a big if - they came together to vote against Tony Blair en masse they would easily overturn his majority of 66.