A biography of the English mathematician Alan Turing, who was one of the inventors of the digital computer and one of the key figures in the breaking of the Enigma code, used by the Germans to send secret orders to their U-boats in World War II. Turing was also a homosexual in Britain at a time when this was illegal, besides being a security risk.
| Actor | Role |
|---|---|
 Derek JacobiAlan Turing | Alan Turing |
 Alun ArmstrongMick Ross | Mick Ross |
 Blake RitsonChristopher Morcom | Christopher Morcom |
 Prunella ScalesSara Turing | Sara Turing |
 Harold PinterJohn Smith | John Smith |
| JJulian KerridgeRon Miller | Ron Miller |
 Richard JohnsonDilwyn 'Dilly' Knox | Dilwyn 'Dilly' Knox |
 Amanda RootPatricia 'Pat' Green | Patricia 'Pat' Green |
 William ManneringYoung Alan Turing | Young Alan Turing |