The findings of a judicial review into the dropping of a corruption inquiry into BAE Systems' Saudi arms deals will be revealed on Thursday.
The High Court has ruled that the Serious Fraud Office (SFO) acted unlawfully by dropping a corruption probe into a £43bn Saudi arms deal.
During a two-day hearing in February, campaigners argued that the Serious Fraud Office (SFO) had acted illegally by cutting short its investigation.
Defence firm BAE was accused of making illegal payments to Saudi officials to secure contracts but the firm maintains that it acted lawfully.
The SFO said UK national security would have been threatened by the probe.
The SFO said national security would have been undermined by the probe.
Accused of making illegal payments to Saudi officials to help secure the deals, BAE maintains it acted lawfully.
The Campaign Against Arms Trade argued that the decision was illegal under an international anti-bribery convention.
The SFO was looking into how BAE won a £43bn deal to supply jets to Saudi Arabia - the so-called Al-Yamamah contract - in the early 1990s.
National security
In December 2006, the attorney general Lord Goldsmith announced that the SFO was suspending its inquiry.
He said continuation would have caused "serious damage" to UK-Saudi relations and in turn threatened national security.
The Campaign Against Arms Trade (CAAT), which sought permission for the judicial review, argued that the decision was illegal under the Organisation for Economic Cooperation and Development's (OECD's) Anti-Bribery Convention.
"This is expressly forbidden under Article 5, which rules out the termination of corruption investigations on grounds other than the merits of the case", CAAT said in a statement at the time of the hearing.
"Signatory governments specifically undertake not to be influenced "by the potential effect [of an investigation] upon relations with another State."
Confidential memo
Saudi Arabia is reported to have threatened to cancel a further deal with BAE to supply it with Eurofighter Typhoon aircraft and withdraw diplomatic cooperation unless the SFO investigation was stopped.
During the hearing, the court was shown a confidential letter from BAE Systems to the attorney general in which the company urged it to stop the SFO investigation.
BAE argued it would "jeopardise" the multi-billion pound Typhoon deal and "seriously affect" relations with the Saudi kingdom.
The OECD said last month that it was launching its own investigation into the decision to drop the SFO inquiry.
