This is the post ww21 British 5,000lb HC bomb (a larger version of the Mk.6 1,000lb bomb), developed for the Canberra and Valiant bombers. It was dropped in trials but its development was cancelled due to cost in 1952.
The tail, with is extended fins, is designated as "tail unit for HS/HA release" (High Speed/High Altitude) and was also studied to equip the version of teh 12,000lb Tallboy intended to be carried by the Vulcan and Victor bombers (project also canceled).
The bomb is now on dsiplay at Solway Air Museum at Dumfries.
Here are other photographs of this same bomb from different angles:
View attachment 205216 View attachment 205218