SECURITY guards last night thwarted an attempt to bomb Britain's

biggest building.

In what was the second bomb plot to go wrong in London at the weekend,

they challenged two men, one armed, who fled from a transit van packed

with explosives at the 800ft Canada Tower on Canary Wharf, in Docklands.

The men escaped in another van, found later by police two miles away

in Bethnal Green, east London.

Police evacuated a large area of the Isle of Dogs after bomb squad

officers used a robot to blow the doors off the first van to

investigate. A large explosive device was found inside.

The guards at Canary Wharf had spotted the blue transit van as it

pulled up at about 8pm under the railway station. When they went to

investigate two men got out, and one, his face covered, produced a gun.

No shots were fired.

Buildings nearby were evacuated, including the offices of the Daily

Telegraph, and roads were sealed off.

A hunt was already under way in London for a terrorist bomber on the

run following the shooting of a police officer, and a similar incident

with a lorry.

Detectives believe a major IRA bomb attack was thwarted when two

uniformed officers stopped the lorry carrying a ''vast'' quantity of

explosives and other bomb-making equipment on Saturday.

One of the officers, PC Ray Hall, was injured when he was shot in the

head and back by the two terrorists in the lorry as they tried to escape

on foot.

A man was yesterday being held at Paddington Green police station

under the provisions of the Prevention of Terrorism Act.

In Northern Ireland the outlawed Ulster Freedom Fighters have vowed

more terrorist attacks after one of the worst periods of violence this


Three civilians and a police officer were killed over the weekend, and

the centre of Coleraine devastated by an IRA bomb.

Among the victims was Mr John Lovett, a 72-year-old Second World War

veteran, one of three men murdered in a UFF gun and grenade attack on a

bookmaker's shop.

Sir Hugh Annesley, Northern Ireland's Chief Constable, will meet other

police and Army chiefs this morning.

The UFF, regarded as the terrorist wing of the Protestant Ulster

Defence Association, says it will counter IRA attacks and claimed the

murders at the betting shop were in retaliation for the IRA bomb in


One person was critically ill and another said to be in a serious

condition, among 12 people, including two Protestants, wounded at James

Murray's betting shop in the Oldpark Road district of North Belfast.

A gunman fired more than 40 shots and then another man flung a grenade

among the dead and wounded.