Blast proves wisdom of reinforcing No 10: Charles Oulton reports on recent security improvements in Downing Street

THE RECENT decision to move John Major's office from Downing Street to Admiralty Arch while his office was made more secure was fully justified last night.

The Prime Minister has only just returned to work at Downing Street, the scene of a mortar attack in February 1991 when the IRA came close to destroying the centre of government.

It was this attack that prompted the decision to make Downing Street, and its windows in particular, more secure. At the time, Mr Major played down the attempt on his life, which happened during a meeting of his Gulf war Cabinet. He suggested the meeting adjourned to another room, and later ordered cold meat after telling a waitress that he had not managed to get any lunch.

But the IRA had struck a nerve.

It had managed to launch a mortar bomb from a white transit van only 200 yards (182m) from where the Prime Minister was sitting, and security chiefs decided they had to act.

When Mr Major returned from holiday in Spain last August, he was moved out of Downing Street while workmen moved in.

Until the mortar attack, Downing Street had been considered secure. The front door of No 10 was steel-reinforced, while metal and explosive detectors were discreetly placed. The fabric of the building had been stripped, reinforced and rebuilt. The security was so effective that the brunt of the blast of the mortar attack was absorbed by reinforced brickwork and specially protected windows. In addition, there were blast curtains below the level of the window, which formed a second barrier.

Now that the windows have been reinforced, the building is considered as bomb proof as possible. However, despite the security measures, the IRA has managed to breach the cordon outside Downing Street again. That will be the problem confronting security officials this morning. They have made the windows more secure, but access to Downing Street is still open to all.

When the IRA carried out a second attack near the Ministry of Defence last January, they placed a briefcase bomb next to a car parked in one of the few streets with parking meters. MPs demanded an end to such unrestricted access, but in the end, they lost the argument. Whitehall is a main thoroughfare of London, and until something is done about it, the IRA will continue to find it as easy to launch attacks from outside the prime minister's home as it does anywhere else in Britain.