The former head of Britain’s arms export agency was issued with a subpoena two weeks ago by US authorities investigating allegations of corruption at BAE Systems, highlighting their determination to pursue a case that the UK has dropped.

Alan Garwood, now BAE’s business development director but who until last year was in charge of export sales at the Ministry of Defence, was served with a subpoena by Department of Justice officials at the end of May. Mr Garwood was changing aircraft at Miami airport.