London — The violence of the illegal Irish Republican Army's terrorist campaign is having its impact on life on the British mainland in ways that go well beyond the explosion of bombs.
Politicians at Westminster are being forced to rethink their attitudes to some aspects of the Northern Ireland problem. And citadels of the English way of life are being threatened.
Catalyst of these sudden reassessments was the car-bomb attack on Harrods department store last Saturday in which five people were killed and nearly a hundred injured.
Prime Minister Margaret Thatcher's government is coming under pressure to ban Sinn Fein, the political wing of the IRA - a move that had been rejected up to time of writing.
Even more insidious in its implications has been a rising demand, in the wake of the outrage at Harrods, for greater social control to combat terrorism. Some members of Parliament have urged Home Secretary Leon Brittan to consider requiring British citizens to carry identity cards. Mr. Brittan says he recognizes the argument but opposes the idea.
Instead, Londoners can see a much higher police presence in the streets. Brittan has ordered 700 more police onto patrol, many with sniffer dogs trained to detect explosives. In the past week it has not been unusual for motorists to be diverted a mile or two from their normal routes because of police checks in the midst of London's pre-Christmas traffic.
Pressures to ban Sinn Fein reflect a growing belief that the terrorists are hypocrites as well as men and women of violence. When the IRA publicly apologized for the Harrods bomb, saying it had been approved by its ''army council,'' there was widespread skepticism as well as revulsion at what Mr. Brittan called its ''nauseating hypocrisy.''
But banning Sinn Fein (including its leader, Gerry Adams, who won a seat in the British Parliament last June) would be difficult. Secretary of State for Northern Ireland James Prior has pointed out that Sinn Fein, by changing its name, could again begin to operate legally. And some observers contend that banning it would give it a propaganda coup, enabling it to assume a martyr role both at home and with its supporters overseas.
One strong possibility is that there will be much stricter control of the acceptance by television and radio of Sinn Fein and IRA statements. It is widely felt the republicans have been manipulating the news media.
Contributor Alf McCreary reports from Belfast:
Leaders of Sinn Fein were consulting lawyers in Belfast Tuesday after a major British television documentary claimed to show direct links between their ostensibly political organization and the illegal Provisional IRA.
Members of Sinn Fein repeatedly deny any links with the Provisional IRA, which is carrying out a campaign of violence to drive the British out of Ulster and to unite Ireland by force. Yet Sinn Fein leaders do not disown violence totally.
Gerry Adams, who became national president of Sinn Fein (''ourselves alone'' in Irish Gaelic) on Nov. 13, recently said he neither condemned nor condoned the recent kidnapping of Don Tidey, the British businessman who was abducted by IRA gunmen in Dublin and held for three weeks. During a shoot-out with Tidey's captors Dec. 16, two members of the Irish security forces trying to rescue him were shot dead. Adams said the IRA gunmen ''had been doing their duty.''
The IRA's policy was outlined chillingly two years ago by Danny Morrison, the Sinn Fein publicity director. He pointedly asked members at the party's annual conference in Dublin, ''Who really believes that we can win the war through the ballot box? But will anyone here object, if with a ballot paper in this hand and an Armalite (rifle) in this hand, we take power in Ireland?''
At this year's conference, Adams deliberately praised ''the freedom fighters - the men and women volunteers of the IRA.''
The hour-long British television program concentrated on Adams' career and his republican background. Coming only two days after the Harrods blast, it had a dramatic impact on British and Irish audiences.
Adams, however, described the program as ''black propaganda.''
The Rev. Ian Paisley, leader of the Democratic Unionists and a long-time vociferous opponent of Irish republicanism, commended ''the courage'' of those who made the program as well as ''those who took part and who exposed the villainy of the IRA and Sinn Fein.''
The statement from the Provisional IRA after the Harrods bomb - claiming the operation had not been authorized by the ''army council'' and saying there would be ''no repetition of this type of operation'' - highlighted the strains within the republican movement. It is thought that members of the movement are well aware that such an outrage is counterproductive at a time when Sinn Fein has been trying to build its electoral image in Ireland.
Sinn Fein has been placed on the defensive not only by the political aftermath of the London bombing but also by the IRA murder of two members of the Irish Republic's security forces. But it still aims to contest the election next year for the European Parliament.
Last June it polled 102,000 votes throughout Northern Ireland during the elections for the London Parliament. But it is thought that many young people were protesting against unemployment and other social conditions rather than showing their support for a policy of the ballot box - and the rifle.