| Episode cast overview, first billed only: |
 | Stratford Johns | - | Det. Chief Supt. Charles Barlow |
 | Frank Windsor | - | Det. Insp. John Watt |
 | John Welsh | - | Asst. Chief Constable William Calderwood |
 | John Barron | - | Deputy Chief Constable Austin Gilbert |
 | Glyn Houston | - | Det. Supt. Arthur Jones |
 | Gilbert Wynne | - | Det. Con. Reg Dwyer |
| David Quilter | - | PC Tanner |
| Robert Keegan | - | Bob Blackitt |
 | Bernard Archard | - | HM Inspector of Constabulary (I) |
 | Patrick Cargill | - | Chief Constable Hamilton |
| Dudley Jones | - | Chief Constable William Howells |
| Charles Morgan | - | Det. Supt. Mortimer |
| John Law | - | Chief Supt. Dunkerley |
| Peter Forbes-Robertson | - | Supt. Grey |
 | Kenneth Benda | - | Chief Constable Everett |
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