Sylvia Syms (Karen Ballard) and Basil Dignam (Prof. Ballard) appeared together a decade earlier in Victim (1961).
Both Roy Kinnear (Bill Marks) and Lance Percival (Carl Gardner) can boast of Beatles connections. Kinnear appeared in the Beatles movie Help! (1965) and in John Lennon's film How I Won the War (1967). Percival provided the voices of Paul and Ringo in The Beatles (1965), and later voiced Old Fred in the animated Beatles film Yellow Submarine (1968).