|Only two handful of
aircraft were ever designated Mk. XX and they were both prototypes for
other marks. The first was DP 845. Initially a Mk. IV, it was
re-designated a Mk. XX shortly after its maiden flight on 27 November 1941
and was later refitted to be the prototype Mk. XII. The Mk. IV designation
was taken over by the PR Type D.
The second Mk. 20, DP 851, initially had a Griffon II engine and made its first flight in August 1942. In December it was refitted with a Griffon 61 and re-designated as a Mk. 21 initial prototype.