Lyneham Lad, see page 258.
http://www.scienpress.com/Upload/JCM/Vol%204_1_15.pdf
"The D5 missile has the capability of carrying either Mk 4 or Mk 5 re-entry vehicles as its payload. The D5 re-entry subsystem consists of either Mk 4 or Mk 5 re- entry vehicle assemblies attached by four captive bolts to their release assembly and mounted on the ES.
STAS and pre arming signals are transferred to each re-entry vehicle shortly before deployment through the separation sequencer unit. When released, the re-entry vehicle follows a ballistic trajectory to the target where detonation occurs in accordance with the fuse option selected by fire control through the preset subsystem.
The re-entry vehicle contains an AF&F assembly, a nuclear assembly, and electronics.
The AF&F provides a safeguard to prevent detonation of the warhead during storage and inhibits re-entry vehicle detonation until all qualifying arming inputs have been received. The nuclear assembly is a Department of Energy (DoE) supplied physics package........."