| Detective Inspector Gregory | |
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| Leopold Dryden | |
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| Joan Dryden | |
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| Rodney Fleming | |
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| Julian Caird | |
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| Guy Bannister | |
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| Poppy Levine | |
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| Herbert Evans | |
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| Sydney Parsons | |
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| Sir Herbert Farquharson | |
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| Chief Commissioner | |
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| Hannen Swaffer | |
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| Vernon Bartlett | |
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| Eric Dunstan | |
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| Gillie Potter | |
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| Elisabeth Welch | |
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| Eve Becke | |
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| Gershom Parkington | |
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| Percival Mackey | |
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| Joseph Higgins (uncredited) | |
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| Police Doctor (uncredited) | |
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| Foreigner (uncredited) | |
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| Weisskopf (uncredited) | |
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| Man on BBC Reception Desk (uncredited) | |
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| Detective (uncredited) | |
|---|
| Peter Ridgwell (uncredited) | |
|---|
| Wife's Lover on Broadcast (uncredited) | |
|---|
