It’s interesting delving into the production history of this particular story, since the televised version (and I suspect from the notes regarding the differences, John Dorney’s adaptation here) had a number of changes made from the original script. Doctor Who fans may see the irony in it being John Lucarotti who rewrote the script! (Look at the history of The Massacre or The Ark in Space, if you don’t know why.)
Not knowing any of this going into the audio, to me this is one of the better episodes, even if it does rely on one hell of a coincidence. All it would need is for Dick Treading to be the doctor on duty that evening rather than David Keel, and the whole thing falls apart! However that sort of coincidence was the meat and drink of 1960s spy series.
Ken Bentley and the team pull this above its B-movie roots, with some nicely contrasting voice work from the different parties searching for the goods. There is a certain amount of cliché to it, but it’s all done with such panache that it works well. There is the odd loose end but that’s almost to be expected.
Verdict: The Avengers doing what they do best. 8/10