Hunting-Clan Air Transport was an independent airline set up after World War II. Operating mainly from Luton Airport, and latterly from Manchester, it had routes from the UK to many African nations and, as the stamp suggests, to Gibraltar. It had a fleet of 15 planes, of which 12 were Vickers Vikings.
The Vickers Viking was a twin engined, short ranged jet modelled by the Vickers organisation on their WWII Wellington Bomber. It was specifically created as a passenger plan. In total, 163 Vikings were built and they were widely used by European airlines and a small number of air forces.