ONE small bomb, strategically placed near Europe's busiest rail

junction, and a telephone call to a television station by a person with

an Irish accent brought commuter chaos to London yesterday as the IRA

continued its mainland Christmas campaign of creating maximum disruption

with minimal risk of capture.

It was revealed last night that, as London tried to get back to

normal, the terrorists were adding to the misery by making hoax warning

calls.

Although the IRA caused chaos, it failed to bring the capital to a

halt. The public acted with stoicism as they tried to get to work to

prove to the IRA that it would not win.

However, with everyone expecting the campaign to continue at least

until Christmas, police last night urged the public to turn their anger

into action by reporting anything suspicious.

Nobody was injured in yesterday's explosion and little damage was

caused when the bomb went off at 5.57am near a track 300 yards out of

Clapham Junction, south London, a major artery for the morning rush

hour.

The bomb, allied to a telephone call to TV-am 10 minutes earlier

claiming a device had been placed in a mainline station, was sufficient

to cause misery for about one million commuters and cost an estimated

#46m in lost business.

All 13 major mainline stations in London, and the Underground stations

that serve them, were closed for up to five hours until searches failed

to uncover any other devices. Roads were packed solid as commuters took

to their cars.

Among the millions whose journeys were badly disrupted was Transport

Minister Malcolm Rifkind, travelling by rail to London from Edinburgh.

Mr Rifkind urged the travelling public to be vigilant, but conceded it

was impossible to give complete protection against attacks like

yesterday's bombing.

''You cannot guarantee that every bit of railway line in the UK can be

permanently watched or guarded.''

Although there were no injuries, the Prime Minister said he was

appalled by the attack.

Passengers on a train leaving Clapham Junction had just heard a

message saying there was a bomb alert at Waterloo and they were

returning to Clapham when there was a flash and an explosion about 50

yards away. The train rocked but nobody was injured.

Although nearby residents were awoken by the explosion, it was clear

the device was tiny by IRA standards.

Hundreds of workers were congratulating themselves in getting into

their offices by 9.30am, only to find that they had to stand on the

pavement for two hours following a bomb scare at the Stock Exchange

tower. It was one of the hoax calls made yesterday to add to the

disruption.

The explosion near Clapham followed a weekend of firebomb attacks by

IRA active service units on the mainland. Three devices exploded at the

Brent Cross shopping centre in north-west London on Saturday and another

went off in the National Gallery on Sunday.

Last night, Metropolitan police assistant commissioner for specialist

operations William Taylor urged the public to keep a close watch at

home, in the office, or while travelling for anything suspicious.

While some hoax calls were made by terrorists, he said many others

were being made by individuals for their own selfish purposes. Mr Taylor

reminded the public that sentences of up to four years had been handed

out for such calls.

Northern Ireland Secretary Peter Brooke yesterday described the IRA as

''barbarians'' for their attack on the National Gallery.

The gallery is in his Westminster South constituency and 30% of the

working population whose rail journeys were disrupted yesterday

travelled through the area, Mr Brooke said in Belfast.

* The IRA terror campaign should be countered with a ''beefed-up''

national police agency, an expert in counter-terrorism said yesterday.

Professor Paul Wilkinson, director of the Research Institute for the

Study of Conflict and Terrorism, said the fragmented structure of the

police -- with 43 different forces in England and Wales -- was

handicapping the effort to catch the bombers.