London — After an interval of four years Irish republican terror has returned with a vengeance to the streets of London. The signs are that it will stay there for some time, as the Provisional wing of the illegal Irish Republican Army (IRA) tries to regain political ground lost when the Maze prison hunger strike collapsed a month ago.
According to Whitehall sources, the IRA has resorted once again to a campaign of bombing in the British capital as a direct result of its failure to force the Thatcher government to grant political status to Maze detainees.
The first two IRA targets were military. A bomb blast outside a Chelsea Army barracks was followed a week later by a bombing that maimed Lt. Gen. Sir Steuart Pringle, commandant of the Royal Marines.
A third attack shifted to a civilian target - the crowded shopping streets of central London. A bomb disposal expert was killed trying to defuse an explosive device in a cafe. Another device in a department store was successfully defused.
If the aim of the bombers was to panic Margaret Thatcher and her ministers into making concessions to the IRA, there is no sign of this happening. The prime minister has continued to issue stern ''no compromise'' statements. Home Secretary William Whitelaw has condemned the attacks and called on the London public to remain alert and steady nerved.
Mr. Whitelaw's officials are suggesting that the bomb attacks, reminiscent of a terror campaign in the mid-1970s, are designed as much to buttress the morale of the IRA rank and file as to intimidate the government. Reuters reports the IRA has also said it is waging economic war on Britain by disrupting pre-Christmas shopping.
The failure of the Maze hunger strike was a major setback to the republican cause, and something was needed to convince junior members of the movement that there were still ways to put pressure on the Thatcher administration.
Scotland Yard antiterrorist specialists believe a team of about six IRA bombers are at work in London.
The pattern up to now has been to give no warning of bomb attacks on military targets. There was a warning before the Oxford Street blast, in line with the IRA contention that its aim is not to kill civilians.
The effect of the new terror campaign on British politicians has been to close their ranks and cancel out party differences. Labour and Social Democratic opposition spokesmen have joined Thatcher ministers in total condemnation of the outrages.
A particularly nasty aspect of the attacks has been the understandable tendency of Londoners to hold in suspicion anyone speaking with an Irish accent.
Police have asked landlords to report arrivals and departures of Irish guests. Irish community leaders in London are saying that it is unfair of the police to use such tactics when only a tiny group of people is responsible for the bomb attacks.
While London braces itself for a new season of political bombings, politicians in the Irish Republic and Britain are working hard to develop a new strategy to deal with the tensions whipped up by the terror campaign.
Mrs. Thatcher will shortly meet the Irish prime minister, Dr. Garret FitzGerald. They will discuss cross-border cooperation between police and Army in the republic and Ulster. They also want to arrange closer political cooperation.
Mrs. Thatcher and Dr. FitzGerald are hoping that the London bombers can be traced rapidly and the campaign of violence quenched. But Scotland Yard, while hopeful that this will happen, acknowledges the difficulties of finding half a dozen shrewd and ruthless terrorists in a metropolis of 10 million people.