No harm done by hoax call - PM
David Cameron has described receiving a call from a hoaxer amid an investigation into how Downing Street security was breached.
The Prime Minister said he was out walking with his family yesterday when the call came through on his BlackBerry, just hours after a similar trick was played on GCHQ chief Robert Hannigan.
However, Mr Cameron said he quickly hung up after the man on the end of the line admitted: "It's a hoax."
"These things do happen from time to time. It's right when they do we properly look at security," Mr Cameron said after delivering a speech in Hampshire.
"What happened on this occasion - and it's the only occasion it's happened in this way to me - having had a day trip to Saudi Arabia, I was taking my family for a nice walk, I had Florence on my back to add to the exercise regime.
"My BlackBerry went in my pocket, it happened to be a conference call, a voice came through I didn't recognise. This voice said he was sorry to wake me up, which I felt was strange as it was 11am. I rapidly asked 'Who is it?' and the voice said 'It's a hoax call', so I pushed the red button on the BlackBerry.
"No harm was done, no national security was breached. It's right we put into place systems to weed out hoax calls."
Reviews are being held into procedures at both Number 10 and GCHQ after the incidents. An initial call to the eavesdropping agency saw a mobile number for director Mr Hannigan disclosed.
A caller to Downing Street claiming to be Mr Hannigan was then connected to the Prime Minister.
It is not known if the same person was behind both hoaxes, but the man claiming responsibility for tricking GCHQ rang the Sun newspaper to confess his actions.
"I've just made complete monkeys out of GCHQ. I've got the mobile number of the director," he told the paper.
"What's more, I am off my face on booze and cocaine."
He added: "I'm definitely going to do it again. It was so easy."
The Sun reported that the man telephoned Mr Hannigan claiming to be an ITN journalist, but said the director was suspicious and ended the call.
The Government said the mobile number provided was not a secure line used for classified information. A notice has gone out to all departments to be on the alert for hoax calls.
A Number 10 spokeswoman said: "There is a process for the handling of calls to the Prime Minister. not all the elements of that process worked on this occasion.
"There was nothing disclosed in the first call that necessarily triggered or generated the second call."
Asked whether the hoaxes could have broken the law, she added: "Our view is that there is no criminal offence."