'Be on your guard'

Metropolitan Police Commissioner Sir John Stevens today urged the public to be vigilant against potential terrorist activity over the festive period.

The warning comes as hundreds of thousands of last-minute shoppers pack Oxford Street and as pre-Christmas sales entice many more to the West End.

Speaking on BBC Radio 4's Today programme, Sir John said: "The threat is different in terms of suicide attacks. The activity and the actual threat has taken a quantum leap since September 11. Everyone needs to know that."

Asked whether activity by the security services had prevented terrorist incidents over the last year, Sir John said: "That is absolutely right, there is no doubt about that. The hard work has been successful, but we must not be complacent. We really must be vigilant."

Sir John was asked about comments by US homeland security director Tom Ridge, who warned that terrorists were planning attacks similar in scale to September 11.

He warned that while he was not in receipt of warnings of that nature, the security level in this country was raised six weeks ago "for good reason".

Sir John said: "Six weeks ago the necessary actions were taken, we have raised our level. There is an immense amount of activity going on even as I speak in terms of ensuring that people's security is there and more of that will go on over Christmas and the New Year."