Over the past 10 days Sinn Fein has been doing all it can to blur the obvious and compelling parallels between the IRA terrorist campaign of 1969-1997 and the London bomb attacks. There is more than a touch of special pleading in their approach.

It’s natural for reformed terrorists to put themselves on a different moral plane from those terrorists who come after them, but by denying the parallels they also deny us the lessons of history.

In the immediate aftermath of the attacks, Gerry Adams offered his “sympathy and solidarity” to the prime minister and the people of London. Naturally he didn’t take the obvious opportunity to express regret for the 112 deaths caused by the Provisional IRA in Britain.

In his column in The Irish News, Jim Gibney, a former Adams aide, condemned the attacks and said that no cause could be served by such tactics. But Gibney took a different tack in November 1991 at the funeral of Frank Ryan, an IRA volunteer, who died with Patricia Black, his 18-year-old accomplice, as they transported a bomb to a concert being given by a military band in St Albans.

In his oration at Ryan’s graveside, Gibney praised the bombers’ determination and drew political capital from their deaths. He said that “even by their own admission, the British intelligence apparatus could not detect them. How could the British government hope to overcome such dedication, how will they defeat this invisible force?” Black and Ryan were not suicide bombers, but Gibney’s words could easily have been spoken in obituary to Shehzad Tanweer, Mohammad Sidique Khan, Hasib Mir Hussain and Jermaine Lindsay, the four young Islamist terrorists who blew themselves up last week.

In both cases, families and friends were shocked by the terrorist links of the dead. Ryan had been born in England of Irish parents and spoke with an English accent. He went to live in Belfast, where he fell under the influence of extremists and joined the IRA. Although his family knew he had developed republican views, they had no idea he was involved in the IRA.

Black, from west Belfast, also joined the IRA in secret and told her family that she was going to live in Dublin, instead travelling to London to take part in the mainland bombing campaign.

Gibney argues that there was a clear moral distinction between both sets of bombers, because, unlike Al-Qaeda, which is suspected to be behind the London bombs, the IRA never set out deliberately to “kill innocent people”. However it is undeniable that the IRA was always prepared to risk killing innocents, and 516 of its 1,706 victims were civilians. The list of “legitimate” targets included retired members of the security forces, civil servants, people who sold bread or petrol to police officers, and telephone engineers who repaired lines on military bases. Unionist politicians were murdered if the IRA didn’t like their public statements. At times it seemed that anybody who was not a republican was liable to be killed as a collaborator.

Even if the IRA’s own flexible definition of what constituted a “legitimate target” is accepted, many bombs went off without warning despite the risk to civilians, including the attack on the Grand hotel in Brighton and the Enniskillen poppy-day massacre.

In other cases the IRA made the warning times too short for bombs to be defused, with horrific results.

No, the real difference between the IRA and Al-Qaeda was not one of moral scruple, but of political intent. Republicans envisaged a campaign ending in political negotiations, whereas the Al-Qaeda leadership, in so far as we can make out from Osama Bin Laden’s statements and fatwas, is seeking to destroy western democracies and establish Islamic regimes throughout the world, starting with Saudi Arabia.

The Islamist movement predates the Iraqi war. It originated in the fall of the Ottoman empire after the first world war and defined itself in opposition to western and pluralist ideas. It finally hit the world stage when, with assistance from America, it led the successful resistance to the Soviet Union in Afghanistan. It now appears to be a loose alliance, appealing to Arab nationalist and Islamic sentiment, rather than a unified and disciplined movement.

The British government always realised that negotiation was possible with the IRA and attempted it at regular intervals throughout the Troubles. By contrast, it is hard to think of a way to negotiate with the diffuse Al-Qaeda leadership, whose aims are so all-encompassing.

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