Mr Williams' family has told the inquest they believe he may have been killed by an agent "specialising in the dark arts of the secret services".
Then he wouldn't have been left in a bag in a rented flat where he was bound to have been discovered. He might have been left, dead, in an extremely compromising position. Or simply disappeared.
If you accept the (widely accepted) premise that SIS do actually run around in tuxedos, drinking martinis (shaken not stirred) and killing people.