British Increase Security After IRA's Mortar Attack

`BUSINESS as usual'' was the official watchword out of 10 Downing Street within minutes of last Thursday's mortar attack by the outlawed Irish Republican Army on the British prime minister's London home. But the attack, which came within yards of scoring a direct hit on the British Cabinet room while Prime Minister John Major and his senior ministerial colleagues were in session, is prompting a massive behind-the-scenes review of security arrangements in London and other British cities.

According to one security source, the two men who drove their van through rush-hour traffic to within 200 yards of Downing Street and lobbed mortar shells toward the Cabinet office, had been in London for some weeks.

``They are still here, and they will be looking for opportunities to strike again. We expect them to use different tactics next time,'' the source said.

On Thursday night, the IRA claimed that it had been plotting the operation for several months.

A statement said: ``Whether the Gulf war goes on for weeks or years, let the British government understand that, while nationalist people in the six counties [of Northern Ireland] are forced to live under British rule, then the British Cabinet will be forced to meet in bunkers.''

A senior Conservative minister said last weekend that it was doubly important for the government to remain ``calm and collected.''

``There is a war on in the Gulf, and Arab terrorist outrages in Britain have been threatened. We cannot afford to show fear or nervousness. That would only encourage our enemies.''

Nevertheless, a drive into central London yesterday revealed plenty of signs that security had been tightened after last Thursday's attack. More uniformed police than normal were on duty, and streets around Whitehall, which is flanked by government offices, were under surveillance from rooftop television cameras.

Vehicles were forbidden to park in Whitehall and nearby Parliament Square.

On Saturday, Major and other government ministers arriving in Scarborough to attend a meeting of the youth wing of the ruling Conservative Party were subjected to what one of the ministers described as ``extreme antiterrorist precautions.'' Police were everywhere and armed marksmen kept rooftop vigil to guard against a possible terrorist attack.

An officer of the Yard's antiterrorist branch told journalists that the crude mortar that fired three bombs at Downing Street (two landed some distance away) had probably been built in a workshop here. The van had been purchased last July.

Similar mortar attacks had been mounted many times in Northern Ireland, but never before in mainland Britain, the officer said.

``The aim of the attack was to obtain maximum publicity for the IRA at a time when its activities in Ulster have been tapering off,'' a security source commented.