Lawyers for Mr Adams told Belfast’s Court of Appeal the convictions should be quashed because his imprisonment under the UK government’s interment policy was unlawful.

Sean Doran QC pointed to documents from the National Archives in London showing that the order for his interment was signed by a junior minister in the Northern Ireland Office, whereas legislation stipulates that it should have been signed by the Northern Ireland Secretary.

Mr Adams was convicted in 1975 of attempting to escape the Maze prison on two occasions, in December 1973 and July 1974.

The appeal was heard by the Lord Chief Justice, Sir Declan Morgan, with Sir Ronnie Weatherup and Sir Reg Weir.