Clifford Evans as Sir Iain Carfax, Jennifer Daniel as Diana Carfax, John White as Dick Culliford, Peter Jeffrey as Philip Skelton
Described as both a televised play and as a made-to-television movie, this BBC 1 production aired on July 8, 1969.
"Martyrs' Hall is a distinguished Cambridge college. The Master, Sir Iain Carfax, has recently left the Cabinet and now enjoys life at his old college with his daughter Diana. The dignified serenity is, however, a cover for the United Kingdom's most important spy cell, 'Codename: Portcullis'. This play concerns the enlistment of a new co-spy and the prevention of a dangerous formula in the germ-warfare arsenal from leaving the country."