Designed by R.K. Pierson and Wallis together, they had teamed on the G.4/31 biplane and
monoplane (the Wellesley) and in Wallis's words "Pierson decides on the design. All I then
have to do is apply the geodetics to it." All he says.
Interestingly, the pair had worked out the engineering of the geodetics for a twin-engined
monoplane before B.9/32 was issued.
Another bit of trivia is that while always associated to B.9/32, K4049 was actually designed
and built to specification B.3/34. The Air Ministry had wanted Goshawks, the Vickers team
preferred the Pegasus. Thankfully, Pierson and Wallis got their way.
The ins and outs are detailed in 21st Profile Vol.1 No.1, "A Beautiful Thing". The Wellington
History, Part One. Vickers Aircraft since 1908 also has an excellent history of the type.