12/31/2024. Remarks by Johan Visschedijk: "The first production order for 180 Type 290 Wellington B.Mk.Is (serialed L4212 to L4391) was placed in August 1936, however, the 38th (L4250) and 39th (L4251) aircraft were completed as prototypes.

Type 298 Wellington B.Mk.II (L4250) (Ron Dupas Collection

The L4250 became the Type 298 B.Mk.II, design of which began in January 1938, but due to delay in the production of the Rolls-Royce Merlin X engine the prototype did not fly until March 3, 1939.

Type 299 Wellington B.Mk.III (L4251) (Johan Visschedijk Collection)

The L4251 became the Type 299 B.Mk.III, design of which began simultaneous to the Type 298 B.Mk.II, but also due to the Merlin X engine production delay, the B.Mk.III prototype first flew on May 19, 1939."