This recording of The Thirty Nine Steps is actually taken from a dress rehearsal, not the production itself - this is for a couple of reasons. Most importantly, the actual recording is of such poor quality that it is a bit of a struggle to follow, I'm actively looking for a better version. Secondly, dress rehearsals for the Mercury Theatre were fairly polished affairs (if they happened at all), and the performances match that of the final production fairly closely.
So there are occasional glimpses into the inner workings of the Theatre (Welles: "Somebody's wrecked my script..." and later "C'mon, this is no dress at all!"). Welles admired Buchan, as his opening eulogy suggests, and both men evidently shared an insatiable appetite for activity. Welles was equally fond of a lively thriller, and The Thirty Nine Steps is one of the liveliest.
Buchan wrote The Thirty Nine Steps, the first of six Richard Hannay novels, in 1915, setting the novel just before the outbreak of the First World War. The title came from his daughter's pride in counting 39 steps at a nursing home, and it became both the title and the 'mystery' to the novel. Much like 'Rosebud' in Welles's Citizen Kane, the search for the meaning of the '39 steps' is the running thread of the play, though listeners may feel that same sense of vague disappointment when the secret is revealed. The novel had been adapted by Hitchcock three years previously, though the two adaptations have a very different feel, Welles's version being a primarily an adventure, more 'fun' than 'funny'.
Orson Welles (Richard Hannay, Marmaduke Jopley)