Thanks to a tip-off over on AiX that it likely shows one of the three B-29s posted to RAF Marham in early 1946 as part of the Project Ruby bombing trials over Germany, this can likely be put down to a simple typo in the original caption.
As a pre-WWII RAF station Marham did indeed have C-Type hangars.
There is a photo in [url="http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201046.html"]Flight[/url] magazine showing B-29 45-21752 over the UK illustrating an article on Project Ruby (The RAF Museum also have a similar photo of her on file).
The Project Ruby report also gives dates, locations and the identities of all three B-29s:
Quote:
In March 1946, three B-29A Superfortresses (45-21747, 45-21750, 45-21751) specially modified to carry either the Tallboy or Grand Slam bombs joined 10 specially modified Avro Lancaster B.Mk. I of No. 15(B) Squadron, RAF stationed at the Central Bomber Establishment, Marham, Norfolk to carry out bomb tests against a selected target.
Scheduled for testing during Project Ruby was the Army Ordnance Deptartment's 22,000 lb ‘Amazon’ earth penetration bomb.
Seven B-17G Fortresses with external wing racks for the 4,500 lb rocket assisted Disney bomb were included in the test schedule.
Project Ruby was followed by Project Harken, the [url="http://www.scribd.com/doc/36187893/B-29-British-Bombing-Tests"]Project Harken report[/url] contains the bombardiers' records of the Farge submarine pen bombing tests while flying the three B-29s listed above.
Oddly, 45-21752 does not appear in either list...
Cheers,
PB