Lancaster powered by Bristol Hercules engines instead of Rolls Royce Merlins. This was a necessity due to the heavy demand for RR engines. I don't know how many Lancs were powered with the Bristol Radial, but it was more than one.
If you have access to the movie "Thirty Seconds Over Tokyo" (maybe on uTube) there are several scenes of the gear retraction sequence - one is from a camera ship flying formation and shows the retraction very clearly..