Orford pagodas

SIR – The odd-looking “pagoda” buildings at Orford Ness in Suffolk (Letters, August 30) were laboratories used by the Atomic Weapons Research Establishment for testing the fusing system for nuclear weapons. The tests used conventional explosives to smash several pieces of plutonium together, forming a single block large enough to sustain a runaway nuclear reaction.

These labs were originally covered by mounds of shingle, the idea being that the energy liberated in an explosion could be safely dissipated in throwing millions of pebbles into the air. Fortunately, this never happened.

When AWRE closed the site down, it was thought advisable to level out the shingle in case the buildings deteriorated and collapsed under the weight of stone. This created their present strange appearance. David Pelly

West Mersea, Essex