Former Prime Minister Baroness Thatcher led a congregation of nearly 200 people at the service on the anniversary of Mr Neave's murder in the grounds of Parliament by the Irish National Liberation Army.

Mr Neave was Shadow Northern Ireland Secretary when he was killed by a car bomb on the ramp leading to the House of Commons underground car park on 30 March 1979 - just yards from the Commons Crypt Chapel of St Mary Undercroft, where Tuesday's service was held.

He was described as a man "whose style was quiet but whose will was steel".

The MP for Abingdon, Mr Neave had also been an army intelligence officer - which made him more of a target for republicans - who escaped from Colditz.

Margaret Thatcher led the congregation at the memorial service

In his address to the service, Lord Mayhew of Twysden, President of the Airey Neave Trust and a former Northern Ireland secretary, said: "To some it may seem odd that a man whom they had every reason to regard as a man of action, and a very private, even mysterious person, should have chosen to enter Parliament.

"But Airey had seen totalitarianism in action. He believed that the only basis for political authority over people was their consent, freely expressed, in Parliament."

For Mr Neave, he said, Parliament was a place where laws could be made which would safeguard personal freedom and extend it.

"His reputation in Parliament was one of pitting himself single-handedly against apparently hopeless odds.

"It was in Parliament that cases had to be made, and arguments fought and won, and not by the decibel level of demonstrations or by violence in the streets. That was the way of the mob, and it was not Airey's way," Lord Mayhew said.

"Freedom was a quiet passion with Airey, someone whose style was quiet but whose will was steel.

"Freedom under the law was the banner beneath which Airey marched to the end."

The service was also attended by Commons Speaker Betty Boothroyd, Tory leader William Hague, Lord Tebbit who was gravely injured in the Brighton bomb blast, and former Northern Ireland secretaries including Lord Prior, Lord Mason, and Mr Tom King.

Current Northern Ireland Secretary Mo Mowlam was represented at the service by Lord Dubs, a junior minister in her department.

The service was conducted by the Reverend Robert Wright, Canon of Westminster and Chaplain to the Speaker.