LONDON (Reuters) - British Prime Minister David Cameron said on Monday security would be reviewed, but no harm had been done, after an apparently drunk hoaxer claiming to be the director of Britain’s eavesdropping agency was put though to his mobile phone.

Britain's Prime Minister David Cameron delivers a speech at Dynamic Earth in Edinburgh, Scotland January 22, 2015. REUTERS/Russell Cheyne

Cameron had been walking near his home in central England on Sunday when his BlackBerry phone rang and he was told there would be a conference call with Robert Hannigan, the head of Government Communications Headquarter, or GCHQ.

“A voice came through, a voice I didn’t recognise. The voice said he was sorry to wake me up, which I thought was strange as it was 11 o’clock in the morning,” Cameron told reporters.

“So I quite rapidly asked ‘who is this?’ to which the answer came ‘it is a hoax call,’ and so I pushed the red button on the BlackBerry which ended the call.”

Hours earlier, GCHQ was also tricked into handing over Hannigan’s mobile phone number after apparently being fooled by the same hoaxer, although the government said it was not a phone used to discuss sensitive or confidential information.

Cameron’s spokesman said security procedures would now be reviewed and all government departments had been put on alert for further hoax calls.

“No harm was done, no national security was breached, but it is important when these things happen to make sure we do everything we can to put in place systems to weed out hoax calls,” Cameron said.

The Sun newspaper reported the unnamed man, who it described as being well-spoken and in his 20s, had called GCHQ in the early hours of Sunday pretending to be a Downing Street aide and saying Hannigan was required to attend an emergency meeting.

He was then given Hannigan’s private mobile number and hours later he called Cameron.

“I’ve just made complete monkeys out of GCHQ,” the hoaxer told the Sun in a phone call afterwards. “What’s more, I am off my face on booze and cocaine. I had some spliffs too. I’ve been up all night. I’m utterly wasted. Hilarious.”

The incident is not the first time that a hoax caller had been able to get through to the phone of a British premier. In 1998, an impressionist pretending to be the former Conservative Party leader, William Hague, was put through to then-Prime Minister Tony Blair.

Blair saw through the hoax immediately, laughing along as the hoaxer offered to lend him an exercise video he had found in a sale.