HOME Secretary David Blunkett insisted last night that a protestor dressed as Batman had proved that a sophisticated Buckingham Palace alarm system does work.

Fathers' rights activist Jason Hatch caused an embarrassing security breach after spending most of the afternoon on a ledge at the front of the royal residence.

The Queen was not at the palace as Hatch, wearing grey tights, black pants and a cape and a mask with pointed ears, began his demonstration just before 2pm.

He unfurled a banner which read: "Super dads of Fathers 4 Justice" and "Fighting for your right to your kids".

In a House of Commons statement, Mr Blunkett told MPs that an alarm system installed at the palace in the wake of the US terror attacks had done its job.

He said that when Hatch, 32, from Cheltenham, Gloucestershire, breached security, he triggered an alarm, and police took immediate steps to protect the palace.

An armed officer took the "entirely correct decision" that Hatch was a protestor rather than a terrorist or dangerous intruder.

Nonetheless, Mr Blunkett said that the Metropolitan Police were looking at how Hatch was able to scale the perimeter in the first place.

He had climbed the outer fence using a ladder - helped by Dave Pyke, dressed as Batman sidekick Robin.

Pyke, 48, said he came down from the ladder after police threatened to shoot him.

After more than five hours on the 25ft high ledge, Hatch waved to the crowds before being slowly lowered to the ground with two police officers in a hydraulic lift.

Sir John Stevens, Metropolitan Police Commissioner, agreed that the incident was embarrassing but said: "The alarms and CCTV operated. The police response was speedy but he got inside the perimeter. It's not good enough."

A Scotland Yard spokeswoman said that a man had been arrested on suspicion of criminal damage and was being held at a central London police station.