When 'Crown Imunity' effectively disappereared the Army had to become 'industrial' . Hence the use of coaches for any trip over twenty minutes.
There has been so much messing about with seating capacitys and licences latley it has become confusing. The old Land Rover Safari was 12 seats, this was to avoid tax regulations at the time, they are now 10 seats. Also if I rember the max now for a group B licence is five or seven.
Some of us still have D1, that is mini bus up to sixteen seats including driver. Now if you wantto drive a minibus it needs a full Class D PCV licence. Once you have that number of seats and weight of vehicle become irelevant.