David Alton, the Liberal Democrat MP, won the support of many mainstream Tory knights of the shires for tougher action.
Many of the 80 Tories who signed his amendment could not be counted on to vote against the Government. But there were more than enough to overturn the Government's dwindling majority and make a defeat inevitable.
The Tory MPs who signed up to the Alton amendment could not be dismissed by the whips as the 'awkward squad' of known rebels, or the 'bastards' who had voted against the Government over the Maastricht treaty.
They are led by Sir Ivan Lawrence, a right-wing criminal barrister and chairman of the cross-party Commons Select Committee on Home Affairs. As chairman of the backbench Tory home affairs committee, Sir Ivan reflects wider Tory backbench opinion, to which Michael Howard has to pay heed.
Mr Alton, an experienced campaigner who had fought to tighten the abortion laws, had lobbied hard for weeks among the Tory MPs.
His campaign on video nasties began after the case of James Bulger, the two-year-old abducted and killed by two juveniles.
Mr Alton was deeply concerned by the unconfirmed reports arising from the case that they had been influenced by seeing video nasties.
That concern was matched by a large mailbag of letters to MPs on all sides seeking action against video nasties. When he had secured the support of nearly half of the Tory back bench, it was clear the Government would have to act.
Others whose support he secured include Michael Alison, a former parliamentary aide to Baroness Thatcher, Ray Whitney, a former minister, and Tory knights such as Sir Fergus Montgomery and Sir John Hunt. Sir Ivan said: 'I haven't supported the Alton amendment because it is perfect but because it calls for positive action to be taken. If it encourages the Government to come forward with a better alternative that deals with the most unacceptable kinds of violence - that does not mean the violence of Schindler's List, it means really horrific stuff - then good. Excellent.
'I want to see the response of a positive kind. It is no use just tightening up the law if people have to prove their age. That won't do.' Sir Ivan's remarks effectively ruled out the preferred option by the censor for the law to be tightened by putting the onus on shopkeepers to verify the age of young people renting videos. Mr Howard made it clear that option would not go far enough to satisfy the public's demands for action. What he meant was that it would not buy off the back bench.
The whips have, unusually, allowed at least one of the rebels to go to Strasbourg today to reduce the rebellion. Sir John Hunt, the MP for Ravensbourne, said: 'I shan't be voting, but there is a lot of concern at constituency level.'
Labour MPs supporting the new clause are led by Clare Short, a former shadow minister. Labour has made it clear it will allow a free vote to Labour MPs, leaving the Government more room to escape defeat, providing Mr Howard produces an effective alternative to the Alton clause to the Criminal Justice Bill.
Leading article, page 15