His single tweak to the Graham Greene script was his speech about Switzerland and the cuckoo clock, which capped the Great Wheel scene with Joseph Cotten and duly passed into film legend. It was also the one time he refrained from taking over a film – either by directing or by rewriting – having met his match in the actual director, Carol Reed. His Harry Lime in The Third Man (1949), charming yet demonic, playful yet monstrous, hints at “some terrible truths about the human condition”, writes Callow. The one time he acted sans plaster or bluster he gave what was probably the performance of his life. Disliking his features, he would often hide behind a false nose (a running gag in this narrative) or other prosthetics unsure of his effect, he would be inclined to thunder.

Partly it had to do with inadequate preparation – too busy to learn his lines – but at a deeper level he was not convinced of what he had to offer.

Callow presents a corrective: Welles strutted all right, but he also fretted. We tend to think of Welles as carrying all before him, bestriding stage and screen with his imposing bulk. Kenneth Tynan, Welles’s most brilliant chronicler and champion, once delivered a verdict on his hero that Callow regards as central: “A fair bravura actor, a good bravura director, but an incomparable bravura personality.” That triumvirate of selves constitutes the burden of One Man Band. As a writer he is more measured than one might expect, and more entertaining than one could have hoped. This is decidedly not the labour of a luvvie. His flamboyant tendencies as a performer have been reined in. Callow has stuck at his task with remarkable patience.

This third part, following The Road to Xanadu (1995) and Hello Americans (2006), takes us only to 1965 the last 20 years of the life are to be covered in a fourth and final instalment. The biographer has been on the trail of his subject for so long (he began writing in 1989) one might have feared he would succumb to boredom or exasperation, familiar hazards to many who had dealings with Welles in his lifetime. S imon Callow’s multi-part life of Orson Welles has become a labour of love – at times a chiding, regretful, head-in-the-hands kind of love, but predominantly one driven by a profound respect.

The one man band