Sebastian is an undisciplined mathematics genius who works in the "cipher bureau" of the British Intelligence. While cracking enemy codes, Sebastian finds time to romance co-worker Rebecca Howard.
Unfortunately the movie Sebastian is not yet available on HBO Max.
| Production | Gerry Fisher | Producer |
| Editing | Brian Smedley-Aston | Editor |
| Production | Herbert Brodkin | Producer |
| Directing | David Greene | Director |
| Production | Michael Powell | Producer |
| Writing | Gerald Vaughan-Hughes | Screenplay |
| Art | Richard Williams | Opening Title Sequence |
| Art | Wilfred Shingleton | Production Design |
| Art | Terence Morgan | Set Decoration |
| Production | Clifton Brandon | Production Manager |
| Directing | Ann Skinner | Continuity |
| Production | John Pellatt | Associate Producer |
| Art | Fred Carter | Art Direction |
| Production | Edith Hamlin | Casting |
| Art | Terence Morgan II | Set Dresser |
| Writing | Leo Marks | Story |
| Camera | Wally Byatt | Focus Puller |
| Costume & Make-Up | Gladys Leakey | Hairdresser |
| Camera | Jimmy Turrell | Camera Operator |
| Costume & Make-Up | Bridget Sellers | Wardrobe Master |
| Art | Alf Pegley | Property Master |
| Sound | Don Challis | Sound Editor |
| Editing | Keith Palmer | Assistant Editor |
| Editing | Jimmy Turrell | Assistant Editor |
| Costume & Make-Up | Bob Lawrance | Makeup Artist |
| Directing | Zelda Barron | Continuity |
| Directing | Gordon Gilbert | Assistant Director |
| Sound | H.L. Bird | Sound |
| Sound | Tristram Cary | Sound Effects |
| Costume & Make-Up | Sue Yelland | Costume Consultant |
| Sound | Gerry Humphreys | Sound |
| Camera | Gerry Fisher | Director of Photography |
| Sound | Jerry Goldsmith | Original Music Composer |
