With the reduction of British overseas bases, the concept of “Rangers” was introduced.
A crew would transit to an overseas airfield (other than the crew’s normal airfield) and fly training sorties from there, thereby simulating working from a dispersed or emergency airfield in various types of terrain (eg snow, desert and tundra) and in the various theatres of war.
A specialist crew chief would be carried in a “sixth seat” to advise on aircraft maintenance / servicing
Rangers were sometimes carried out in conjunction with air exercises in a particular region.
(Note: Some sorties were classified as “Trainers”; this was when a training sortie was carried out from the crew’s normal airfield).