“Washington” was the RAF designation for the famous Boeing B29, one example of which, the Enola Gay, dropped the first atomic bomb on Hiroshima. No B-29s were built for the RAF. All that were received (87 in total) were built for USAAF use many had seen active service before being transferred to the RAF in the early 1950s.
See here and here for more detail
My father M/Nav Arthur Collins was a navigator on the B29 Washingtons at RAF Watton with 192 Squadron in 1956 and 1957. He was previously at RAF Waddington on Avro Lincolns and afterwards on the B29 at RAF Marham. As a service ‘brat’ I enjoyed my time in MQs at RAF Watton living in Dixon Close and travelling by train each day to attend my school at Hammonds Grammar Swaffham
My parents were friendly Flt/Lt Chorlton who was a Washington Pilot and his wife .
“A” Flight 192 squadron were equipt with these, I was with “B” Flight which had 2 B2 Canberra,s and 2 B6,s
Had a flight in one of the Washingtons,local flying!! we landed 7 hours later.
Great squadron, lots of interaction between aircrew and ground crew.