As quoted to me by a very old guide at Duxford during a tour:
"If you open the panels, you'll see that the lower fuselage ribs of our Concorde curve upwards in the middle. This was done to allow her to carry the Blue Steel (I think he said Blue Steel, it was a couple of years back) Nuclear Missile".
No reason to doubt him and his knowledge of the aircraft in the collection was bordering on Jedi Master.
I went on to jokingly ask him for a sit in the Lancaster - and he said sure thing!
Spent half an hour clambering around inside her!
