FOR some considerable time it has been apparent that it was not a question of whether Stephen Byers would resign, but when.

Having for so long survived intense pressure to go, the only surprise is that he chose yesterday for his farewell from the front bench, rather than hang on until the traditional annual round of reshuffles in June or July.

Whatever the timing, few will regret his departure.

By insisting in his resignation speech that he was no liar, Mr Byers appears to be attributing his downfall to the allegations that he misled the public and misled Parliament.

But, for a politician, duplicity is not necessarily a resignation matter.

Mr Byers had to go for committing a gross error of judgement.

Like the rest of the nation, he should have shared the revulsion at his advisor Jo Moore's memo about September 11, and sacked her without a moment's hesitation.

In standing by her, he made a grave mistake from which he was never going to recover. That one decision has cost him his career.

His subsequent failure to control his department's communication team effectively helped seal his fate.

So, too, did his ill-starred performance in charge of the Department of Transport, Local Government and the Regions.

History will remember his 12 months in office for his bold decision to place Railtrack in administration. But it will also remember it for his failure to capitalise on the popularity of that decision by advancing the pace of improvements on our railway network.

We do not envy the challenges facing his successor in picking up the pieces of a transport policy which appears to lie in tatters.

Also called into question throughout this sorry saga is the judgement of the Prime Minister. He was unwise to allow a situation to develop where his Transport Secretary spent most of his time defending his own integrity instead of promoting his Government's programme of reforms.

While it may be a virtue in a normal human being steadfastly to support close colleagues such as Peter Mandelson and Mr Byers in times of trouble, it is not necessarily a quality to admire in a Prime Minister who we expect to put the interests of the country above all others.