The killing of Jean Charles de Menezes when London was gripped by a genuine fear of terrorists was the tragic result of a catalogue of police mistakes.

But yesterday's £175,000 fine for breaching health and safety law is an odd form of accountability as it punishes tax-payers who fund the Metropolitan Police, not its commanding officer.

Predictably, Sir Ian Blair refused to resign while the Premier and Home Secretary rallied behind him.

On this occasion the convincing arguments were heard from Liberal Democrats and Tories who demanded the Commissioner's head.

As the officer in charge, he should be accountable and accept responsibility for serious errors that ended in a death.

Sir Ian's ill-starred reign has been overshadowed by blunders, misjudgements, slip-ups and allegations of cover-ups.

His shameless clinging to the most important policing post in Britain damages the office itself.

Sir Ian should resign or be sacked to make way for an officer who'll do a better job of keeping Londoners safe.