Classic Thriller Sextet

The "Classic Thriller Sextet" is a term coined by Raymond Durgnat for the six consecutive 1930s films which helped established Hitchcock as a thriller director:

The Man Who Knew Too Much (1934)
The 39 Steps (1935)
Secret Agent (1936)
Sabotage (1936)
Young and Innocent (1937)
The Lady Vanishes (1938)

The first five films were made for the Gaumont-British studio. The Lady Vanishes was made for Gainsborough Pictures and distributed by Gaumont-British.

In English Hitchcock, scholar Charles Barr notes the following themes:

with the exception of The Man Who Knew Too Much (where the lead couple are already married), all the films end with the male and female leads characters becoming a couple
with the exception of Young and Innocent, all the films have a strong political dimension
with the exception of The Lady Vanishes (which was an existing scenario written by Sidney Gilliat and Frank Launder), all the films credited Charles Bennett as the primary writer of the screen adaptation
with the exception of The Man Who Knew Too Much (which was an original screenplay based loosely on the Bulldog Drummond series), all the films were loose adaptations of existing novels
with the exception of Secret Agent (which was set in 1916), all the films were set in contemporary Britain and/or Europe