IRA intent on rebuilding campaign: Attack was timed to coinicide with MPs' debate, writes David McKittrick

THE Heathrow mortar attack will be seen as the most emphatic confirmation yet that the IRA is unimpressed with December's Downing Street declaration and may be intent on building its campaign back up to previous levels.

Republicans have always been critical of the Prevention of Terrorism Act and the timing of the airport attack will be seen as a sign of their displeasure at the law. But the main messages are that the violence is to go on and that the Government should reopen its channels of communications to the republicans.

The timing was unusual in that the IRA rarely tries to synchronise its attacks with specific political events. This may be a sign that the organisation will in future attempt to tailor its activities more closely to the political moves of Sinn Fein, its political wing.

A few hours before the airport attack, Tom Hartley, the Sinn Fein chairman, had issued a statement portraying the Government's intention to renew the PTA as a missed opportunity in what he called the peace process. He declared: 'The development of a peace process requires good faith on all sides and a willingness to explore new avenues of debate.'

Mr Hartley said the Government could have signalled its goodwill by scrapping or amending the PTA, adding that such gestures 'would have signalled a determination to move the discussion on to a different plane'.

It is not known whether that last word was intended as a deliberate pun with reference to Heathrow. It is clear, though, that the republicans want to keep the peace process alive as a long-term exercise and that they are seeking some conciliatory move from the Government.

Since December the level of IRA activity in Britain has been low, while in Northern Ireland it has moved away from large-scale bombings and concentrated on attacks on the security forces.

The mortar attack on 10 Downing Street in February 1991 demonstrated the weapon's capacity for staging high-profile attacks on prestige targets. Mortar attacks happen by the dozen in Northern Ireland, but are rare in Britain.

The home-made devices are assembled in secret factories in the Irish Republic and then smuggled into the north or across to England. The use of timing devices means IRA members have time to get clear before the actual attack.

But the devices are notoriously inaccurate. In military terms mortars are an 'area weapon', designed to scatter missiles over a given district rather than to achieve pinpoint accuracy. The IRA uses a range of home-made weapons, which it has sought to improve over the years: the Army calls the current version the 'Mark 12'.

The weapon has been a feature of the IRA's campaign in Northern Ireland since the early 1970s. One caused the greatest single loss of life ever sustained by the RUC, when a missile hit and demolished a crowded police canteen, killing nine police officers, in Newry, Co Down in 1985. The IRA has never, however, succeeded in repeating that blow, largely due to the unpredictability of the weapon.

(Photograph omitted)