Starting life as a float plane it was later converted to a land plane. As noted Imperial Airways were not interested and it was used by Sir Alan Cobham on a survey flight of Africa, leaving Rochester (Short's Factory) in July 1931 and returning after completing some 12,300 miles in September 1931. It ended it's days as an instructional airframe at R.A.F. Halton.
This large passenger-carrying seaplane was intended for operation between Cairo and Capetown. It was considered to be the float-plane equivalent to the Short Calcutta flying boat. There doesn't seem to have been anything particularly wrong with the Valetta except for the fact that, at that time, Imperial Airways considered that flying boats were more efficient than float planes.