The UK's most senior police officer has called for the urgent introduction of compulsory identity cards.
Sir John highlighted the threat from terrorism
Sir John Stevens, head of London's Metropolitan Police, said he used to be "ambivalent" about the idea.
But, he told BBC 1's Breakfast with Frost, he now saw them as "essential" in the fight against terrorism.
The introduction of ID cards has been agreed in principle by ministers - but a decision on making them compulsory has been delayed for several years.
The plan - which could see the earlier introduction of a voluntary scheme - was announced by Tony Blair's spokesman after reports of bitter disagreements within the cabinet over the issue.
The decision was described by civil liberties campaigners as a "humiliation" for Home Secretary David Blunkett, who favours the introduction of compulsory identity cards.
In his interview, Sir John said Britain was currently at its highest ever level of alert because of the threat posed by terrorists.
Both police and the security services were working on the assumption that an attack was "inevitable".
He said ID cards needed to be brought in quickly.
"The sooner it is brought in for us - being somewhat selfish in terms of public safety - the better," he argued.
"It is something I was ambivalent about five years ago, but very much in
"It is absolutely essential in the modern world, the dangerous world we live
in, that we have proper means of identification.
"If we have got a means of identifying people with reasonable certainty - which this is - then that is what
we should be doing."
Sir John - who has overall responsibility for police anti-terrorist activity - said the Met faced an "unprecedented challenge" over security for US President George W Bush's visit to the UK beginning on 19 November.