The British government was mistaken if it thought last December's shabby decision to drop its investigation into alleged corruption around the £43bn Al-Yamamah fighter export deal with Saudi Arabia would end the matter.

The US Department of Justice has decided to launch its own probe into whether BAE Systems, the British defence contractor that is also a large supplier to the Pentagon, has violated the Foreign Corrupt Practices Act. That decision shows the UK government's arguments for suspending its investigation - that it would wreck a vital national security relationship with the Saudis and cost thousands of jobs - for what they are: specious realpolitik and economic excuses.