Pictures of Avro Bison, from the collection of Bob Moorey, copy kindly supplied by his son Steve Moorey.
Please see more pictures at Steve's site: stevemoorey.zenfolio.com
Avro Bison Mk.I, date and location unknown.
Avro Bison Mk.II, date and location unknown. Note that the Mk.II differs from the Mk.I by having it's top wing mounted above the fuselage on struts rather than being directly attached to the fuselage frame.