'Byran Forbes' wrote the part of Knocker White for Richard Attenborough.
André Morell (Marshal) and John Mills both went on to play Professor Bernard Quatermass: Morell in Quatermass and the Pit and Mills in Quatermass.
George Cole and Jon Pertwee were originally planned to star, until Cole left his contract, which resulted in different stars being sought.
The first film of Barry Foster.
The last film of D.A. Clarke-Smith.