THE IRA yesterday returned to London to continue a ruthless campaign

of attacking soft military targets on mainland Britain -- this time in

the constituency of junior Irish Minister Peter Bottomley.

But on this occasion, they adopted a new and worrying tactic for

security forces. The plastic bomb of up to 10lb, possibly Semtex, that

could have killed and maimed scores of people, was buried out of sight

in a flower bed.

As it was, seven people -- all civilians -- were injured in the

explosion at the headquarters of the Royal Army Educational Corps in

Eltham, south London.

''It was a miracle that this was the only cost in human suffering from

this bomb,'' was the initial reaction.

The head of Scotland Yard's anti-terrorist branch, Commander George

Churchill-Coleman, arrived at the scene almost immediately.

As bomb squad and forensic experts searched the area, he declared:

''This may only be the start of several further devices going off in

different parts of the country.''

He added: ''These people are bent on causing destruction and death.''

The tactic of burying bombs was a new one and those responsible for

looking out for IRA terrorist attacks would now have to take this into

account. He issued the warning to all involved in military security.

Most seriously hurt in yesterday's blast was Mr Peter Hills, a civil

servant who heads the organisation to help soldiers, sailors, and airmen

settle into civilian life once they leave the armed forces.

He suffered two fractured ribs as he was blown across a room shortly

before 10am. ''He was a lucky man,'' said Forces' Minister Mr Archie

Hamilton.

Despite the minimum casualty count on this occasion, the 10lb plastic

bomb was a major device by any standard.

Four men and three women were hurt in the blast.

Extensive damage was caused to the Army training headquarters and to

nearby houses, which were shaken to their foundations. Windows were

blown out and glass flew everywhere.

At least one vehicle in a car park near the centre of the blast was

thrown on its side.

A tangled mass of bricks and debris and broken glass littered the

scene around the car park, and a gaping hole was left in the Army

building.

Police fear that possibly two IRA hit squads may be currently

operating in mainland Britain and at least one more in Europe. But they

do not believe yesterday's attack signalled a new offensive by the IRA.

The Provisional IRA admitted responsibility hours after the bomb had

exploded.

The injury toll within the Army headquarters could have been much

heavier had not bomb-proof film been placed across windows a few weeks

ago to prevent flying glass in just such an incident.

The continued attack on soft targets by the IRA follows the explosion

in Deal, Kent, last year in which 11 young Royal Marine bandsmen lost

their lives and blasts earlier this year outside an Army recruitment

offices in Halifax, Yorkshire, and in the centre of Leicester.

Mr Bottomley, Tory MP for Eltham, was quickly on the scene.

''The people who did this are the dinosaurs of Europe,'' he said.

''The key issue is not whether establishments can be 100% secure.

Clearly, that is impossible.

''The key issue is whether this is an acceptable price to pay for a

so-called cause. The people of Ulster do not believe it is.''

The blast happened as Irish Prime Minister Charles Haughey is coming

under increasing pressure to change extradition procedures to ensure

that known terrorists do not find political refuge in the Republic.