Shortly before the trial opened last October, Mr Clark was questioned by Customs about an interview he had given to the Sunday Telegraph in which he appeared to admit 'tipping off' Matrix Churchill about how it should frame its export applications to get round guidelines for trade with Iraq.
In the interview, Mr Clark was reported as saying that his job as trade minister had been to 'maximise exports despite guidelines I regarded as tiresome and intrusive'. He also said that 'it was clear to me that the interests of the West were well served by Iran and Iraq fighting each other, the longer, the better'.
However, when challenged by Cedric Andrew, a lawyer for Customs, Mr Clark denied making the statements. David Leigh, the author of Betrayed: The Real Story of the Matrix Churchill Trial, claims he said: 'The journalist may have transposed what was said during the interview . . . It is balls I would have said that.'
If Mr Clark had admitted making these statements, as he subsequently did in the witness box, the trial would not have gone ahead. Alan Moses QC, representing Customs and Excise, said on 1 October, in the early stages of the trial, that 'if there be any truth in what he was reported to have said . . . then, of course, the prosecution would not go ahead if what he said is accurately reported, and was his attitude at the time'.
When called to give evidence, Mr Clark admitted the 'validity' of the statements made to the Sunday Telegraph but described the idea that he tipped off Matrix Churchill as 'journalistic slang'.
However, he pulled the rug from the prosecution case when he admitted that he had advised a meeting of machine tool representatives, including one of the defendants, Paul Henderson, that any licence application should emphasise the tools' peaceful use.
The advice to omit the potential military use from the application was 'our old friend economical . . . with the actualite'. The three defendants, all former executives of Matrix Churchill, were cleared of illegally exporting equipment for making shell fuses to Iraq.
The book also highlights the role played by Mr Moses, who told the judge the documents that the Government was trying to keep from the court would not 'assist the defence in relation to any foreseeable issue . . . there is nothing in the documents to suggest that the DTI . . . knew that there had been concealment, or that assurances the machines were for civilian or general use, were false . . . There is nothing in the interests of the prosecution to keep these documents from the defence'.
Scotland Yard would not comment yesterday on reports that detectives are interviewing witnesses, and are expected to speak to Mr Clark.