Individual pages for each book listed under John Buchan’s Works contain references to film and play adaptations in addition to the following:

The 39 Steps (1959, Ralph Thomas, remake of the Hitchcock one)

The 39 Steps (1935, Hitchcock)

The Thirty-Nine Steps (1978, Don Sharp)

The 39 Steps (2008 BBC Production)

Huntingtower (1927, George Pearson, B+W, silent)

Huntingtower (1957, TV, Shaun Sutton)

Huntingtower (1978, TV, Bob Hird)

The Three Hostages (1977, TVM, Clive Donner)

Hannay (TV series 1988-9, dir. Ken Hannam)

John Macnab (TV series, 1976, dir. Donald McWhinnie)

Buchan’s filmography on the British Film Institute database

Nigel Deacon has compiled a comprehensive list of JB radio adaptations on his website