... too make the long story short. Britain got locked out of the US atomic-weapons program because of too many spies. So they had to go it alone after WW2 and their participation in 'The Manhattan Project.'
... here we see a fission-implosion device that was used as part of a hydrogen-boosted weapon delivering a whopping 720 kiloton yield in 1957. At the time the Brits rather overstated it as an H-Bomb. Those aren't wheels for Monty Python to deliver it to the gates of the Kremlin; but framework to hold it in place within the bomb shaped casing. While the US gave their various weapons boring numerical designations this product of British engineering was known as the "Orange Herald" ... quite!
... Boris and Natasha would love this photo; as it gives an uncomfortable amount of detail of the firing mechanism for the high-explosive 'lenses' needed to cause implosion of the plutonium core.
... I was embarrassed that it took me so long to realize that the plutonium sphere which is the target of implosion for a fission device is actually hollow and not solid. Simply speaking you take just the right amount of super unstable plutonium, manufacture it into a hollow ball, then instantaneously squish it into a very compact solid ball with a perfectly balanced even synchronized explosion.
... in this cut-away we see that the 'safety' on the device was a whole mess of ball-bearings. In the event of an 'accidental' detonation of the high-explosive 'lenses' (they are called 'lenses' because they focus the explosion) the ball bearings prevent the hollow ball of plutonium from collapsing. Early US devices were armed by inserting a part of the mechanism after the delivery aircraft was in flight and on it's way to the target. Later designs used a mechanical means to prevent t he mechanism from working properly.
... ah yes; this wonder weapon was christened "Violet-Club"
... 1952: the "Blue Danube" , Britain's first atomic-bomb. Only about half the yield (10 kilotons) of the Hiroshima "Fat-Man" weapon.