An early choice was Jack Lord, but the part of McGill eventually went to Richard Bradford, a method actor who was spotted after appearing opposite Marlon Brando in the 1966 movie The Chase.

Unable to clear his name or return to the US, McGill makes ends meet by working as a travelling private detective and bounty hunter based in Britain, living out of his suitcase (hence the title).

Accused of complicity in the defection, McGill was unable to call on Thyssen to clear his name, as his superior had been drowned in a sailing accident, and he was forced to resign from the service amid much negative publicity.

As McGill's diligence nearly blew open this important operation, his superiors had no choice but to make him a very public scapegoat, to maintain the illusion of the LeFarbe defection as genuine.

Because of his unofficial, semi-legal status, McGill often finds himself being hired by unscrupulous clients and unwittingly used for criminal ends, or set up as a fall guy.

On several occasions, characters from his past with US intelligence draw him into dangerous situations; and he can also be blackmailed or tricked into participating in espionage missions, as he is the perfect deniable operative.

It highlighted character-based drama grounded in a cynical view of the real world, making it more akin to the spy novels of John le Carré and Len Deighton.

As a man who feels betrayed by life and his country, he can appear outwardly as surly, moody and uncommunicative, but this masks a sensitive interior.

Unlike most TV action heroes of the time, McGill would not get cleanly knocked unconscious and then recover without effect; Bradford took great pains to depict the character as wounded and concussed.

Guest stars include some ITC regulars such as Roger Delgado, Stuart Damon, Jane Merrow, Basil Dignam, Ed Bishop, Anton Rodgers, George Sewell, Philip Madoc, and John Gregson; and such actors as Barbara Shelley, Rodney Bewes, Felicity Kendal, Rupert Davies, Colin Blakely, Ray McAnally, Bernard Lee, Jacqueline Pearce, Edward Fox, Sam Kydd and Donald Sutherland.

Extras consist of commercial bumpers, both US and UK, a music-only track on one or two episodes, and an interview with series star Richard Bradford where he sometimes vehemently describes the working conditions and former producers of the show.