Sir John Stevens, the Metropolitan Police Commissioner, has demanded a full report by this morning.

The Queen, who is on holiday at Balmoral, was kept informed of the incident. None of the Royal Family was in the Palace at the time.

Jason Hatch, 32, a decorator from Cheltenham, achieved instant worldwide publicity around 2pm when he evaded armed police and climed to the ledge, alongside the first-floor ceremonial balcony.

He wants to highlight the campaign for fathers’ rights of access to their children and demanded to speak to the Prince of Wales or the Duke of York, both of whom have been estranged fathers. He eventually ended his protest after about five hours.

As other protesters from Fathers 4 Justice created a diversion at the main gates, Mr Hatch and an accomplice dressed as Robin scaled the railings with a 10ft extending ladder and reached the roof of an annexe.

While Mr Hatch made his way to the ledge egged on by supporters, his accomplice, David Pyke, agreed to come down when police threatened to shoot him. “The officer said to me: ‘Come down or I shoot’. It was pretty scary,” Mr Pyke said before being taken away for police questioning.

In a Commons statement last night, David Blunkett, the Home Secretary, claimed that the breach demonstrated that new security alarms and cameras installed at Royal palaces had been successful.

He said that an alarm was triggered the moment the protesters erected their ladder.

“An armed police officer confronted the intruders. Within minutes, the external perimeter of the palace had been sealed,” Mr Blunkett defended the judgment of police that the man who scaled the colonnade was a protester rather than a terrorist, otherwise he would have been shot.

Mr Hatch and Mr Pyke planned their protest last Saturday over a pint in a Shropshire pub. They had carried out four reconnaissance missions to the Palace.

Watched by hundreds of onlookers, Batman, in his black and grey costume, unrolled a banner reading “Super dads of Fathers 4 Justice.” He waved his arms and punched the air as he stood on his precarious eyrie. Police officers on the balcony a few feet away tried to talk him down but, when he refused, Palace staff passed him glasses of water.

After three and a half hours, police brought in a cherry-picker truck, and Mr Hatch was eventually persuaded into the hopper at 7.15. He was taken away for questioning by police.

Mr Hatch, who has two children by his estranged wife, has staged demonstrations at York Minster, a Gloucester courthouse and the Clifton suspension Bridge in Bristol.

But his stunt at the Palace set far louder alarm bells ringing.Two recent security breaches have prompted a thorough review of the Royal Family’s safety, and drawn promises that Royal residences would now be more tightly guarded.

Last year Aaron Barschak, a comedian dressed as Osama bin Laden, infiltrated Prince William’s fancy-dress 21st birthday party at Windsor Castle, while Ryan Parry, a Daily Mirror reporter, worked for two months as a Palace footman, gaining access to the Queen and her family.

Although the Palace never discusses security or includes it in its annual balance sheet, the cost of protecting the Royal Family is said to be almost £100 million a year.

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