Bull's killer has never been found. It has always been assumed that his professional execution - he was shot on his doorstep in the back of the head at point-blank range - was carried out by an agent from Mossad, the Israeli secret service, which was desperate to prevent Iraq acquiring the supergun technology. But letters passed to the Independent reveal that he was also deeply worried about the behaviour of the Foreign Office.
The letters are from Bull to Philippe Glibert, deputy general manager and sales director at PRB, a Belgian munitions company. They were both sent on the same day, 31 October 1989.
In them, he complained that the Foreign Office was spreading false stories about him and he had been warned his life was in danger. 'I addressed a blunt memorandum to the Foreign Office on the whole matter,' he wrote. 'I was advised in a letter of an imminent 'accident'.' Following his memo, Bull says 'we were assured that the action was by a 'few irresponsible juniors and did not reflect the Foreign Office views of myself, our companies, the past etc'.'
William Waldegrave, who last week gave evidence to the Scott inquiry into arms to Iraq, was a Foreign Office minister at the time the letters were written.
The breakdown in relations with the Government, Bull said, was a recent occurrence. Until the late summer he had been on the point of receiving state aid to redevelop the old Lear Fan aircraft factory in Belfast. His company, Space Research Corporation, was interested in the plant's carbon fibre facility, vital in the production of nose cones for missiles and ammunition. But the deal did not go ahead - at the time the Government said it was concerned at Bull's Iraqi links. However, according to the letters, that was not the case at all: the Government had known about them.
SRC, Bull wrote, 'worked with the Industrial Development Board and Peat Marwick (Brussels) to develop the business plan. One issue brought up at the outset was the question of acceptability. Was SRC acceptable? Were the Iraqis acceptable? The Northern Ireland authorities were most affirmative on both and were given full background details'.
The Iraqis accepted the business plan and agreed to be a 50 per cent partner, 'but only after they sent their own group . . . to receive assurances from the Northern Ireland authorities that they were welcomed . . ' Bull maintained that it was not the case that SRC sought state backing - it was the Government that wanted to be seen to be investing in a project in Northern Ireland. 'We did not need the money . . . the IDB insisted on the grant for political reasons.'
However, the Government money never materialised. Bull alleged that the intervention of a senior civil servant caused a rethink.
The Foreign Office said: 'The whole question of the supply of arms to Iraq is a matter Lord Justice Scott is pursuing at the moment.' Mr Glibert refused to comment. The Scott inquiry resumes today.
Supergun trial for Italy, page 12