Leading article: David Davis has struck a fine blow for the cause of civil liberties

The Haltemprice and Howden by-election was not, in the end, the spectacular national debate on the state of civil liberties in Britain that David Davis wanted when he dramatically resigned his parliamentary seat last month. But the former shadow home secretary still deserves a generous portion of credit for taking a stand on this issue. The growth of casual surveillance by the state is indeed a cancer in our society. And the steady erosion of our civil liberties by the Government is every bit as dangerous as Mr Davis has been arguing. If this by-election has caused even a handful of people to reconsider the benefits of the proliferation of CCTV cameras, or the merits of ID cards, it will have been worthwhile.

And Mr Davis's campaign coincided with the devastating intervention on the issue of 42 days detention by the former head of MI5, Eliza Manningham-Buller, this week. In her maiden speech in the House of Lords, Lady Manningham-Buller argued that extending the detention period for terror suspects is a bad idea: dangerous in principle and flawed in practice.

It would be difficult to overstate the significance of this intervention. For someone who enjoyed privileged access to all the intelligence on suspected terrorists to come out in opposition of 42 days should surely kill this daft piece of legislation stone dead. The Counter-terrorism Bill will be rejected by the Lords when they come to vote on it in October. At that point, Gordon Brown's only remaining card will be to force it through the Commons again and threaten the Lords with the prospect of bringing the Parliament Act into play. This would be the nuclear option, but, after his painfully narrow victory in the Commons last time round, the Prime Minister would most likely find himself immolated in the resulting blast.

For all these reasons, Mr Davis's victory this week will not have cheered Mr Brown. But Mr Davis's personal campaign has been uncomfortable for his own party leader too. It is no secret that David Cameron was furious over Mr Davis's decision to resign his parliamentary seat and fight a by-election. And Mr Cameron's rapid appointment of Dominic Grieve to fill Mr Davis's place in the Shadow Cabinet was the political equivalent of slamming the door shut on Mr Davis's career.

But the Conservative leader should not rule out a return to front-line politics for Mr Davis. When he resigned last month, the move was written off by many in Westminster as a fit of madness by a politician in the grip of some sort of personal crisis, perhaps even a suicidal fit of pique against the man who beat him to the leadership. But many in the country responded differently. They rather respected this politician who was apparently prepared to jeopardise his political career for something he believed in strongly, even if they did not share his views. Mr Davis managed to pull off the rare trick of being popular, without espousing populist policies. Most politicians nowadays tend to achieve the exact opposite.

But this is not the only reason to recall Mr Davis to the front bench. It is not just that he is a street fighter. Above anything else, Mr Cameron needs more people of modest origins like Mr Davis around him to counterbalance the impression that the Conservative Party is run by a clique of old Etonians. The Conservative leader did not want this particular by-election, but he has an opportunity to profit from it nonetheless.