Before being cast as Professor Bernard Quatermass in
Quatermass and the Pit (1958), he had been the first choice for the role prior to the production of
The Quatermass Experiment (1953) but had turned it down. Following Tate's sudden death on August 23, 1955, he was once again offered the role in
Quatermass II (1955) but turned it down for the second time.
John Robinson was cast in his stead. When
Quatermass and the Pit (1958) was being adapted for the cinema, the producers of
Quatermass and the Pit (1967) asked Morell to reprise his role but, for the third and final time, he declined the opportunity to play Quatermass. On this occasion,
Andrew Keir was cast as the Professor.