The last of four appearances in the series by Roland Bartrop, the others being E7, Diamond S.O.S. (1959), E9 Dead on Arrival (1959), and E18 The Thousand Mile Alibi (1960), in these three episodes he played the character Grimod.
The first of two appearances in the series by Michael Balfour, the other being in E31, A Foreign Body (1960).