I have seen "The Long Memory" twice, and was sufficiently impressed (and like John Mills) that I bought the book when I found it. After seeing the film a second time I then started reading the book. To my delight (that's how I like films) it was close to the film, and I realized that much of the quality of the film, beyond its strong visual imagery of London dockside slums, damaged by the Blitz (you have to know this: there is no sign saying "house flattened by bomb"), and post- war austerity (rationing continued in Britain into the early 1950s!), is directly due to the book author Howard Clewes (about whom little is available on the internet).
Despite not LOOKING like the author described him, John Mills acts the character described by the author, as do the rest of the cast.
The post-World-War-II setting is crucial to appreciating the bleakness of the film. Life was tough then, for many British, and even more so for Displaced People -- war survivors and immigrants from Europe. Petty crime was rife. In fact things were probably tougher than during the flashback sequence to the Depression, when the young Mills character is accidentally drawn into cross-Channel smuggling of wanted criminals, and contraband.
The old "beachcomber's" singing of a traditional English folksong is a haunting addition to the film that does not appear in the book.
