There are 2 movies named The Man Who Knew Too Much, both directed by Hitchcock. This 1934 version is by far my favorite. I know the 1956 remake with Jimmy Stewart and Doris Day is better known and seems to be the preference for most, but not for me. I don't need Doris Day singing Que Sera, Sera, and I think there may actually be such a thing as too much of Jimmy Stewart.
The 1934 version stars Leslie Banks and Edna Best (The Ghost and Mrs. Muir). Peter Lorre also stars and is a stand-out in the role.
The film can be viewed online thanks to googlevideo:
BFI's Sight&Sound prefers this version to the remake:
Aside from its East End setting, the earlier version scores two great points over its remake. One, of course, is Peter Lorre's brilliant, wheedling turn as the oleaginous Mr Abbott. The other is its climax, recreating the Sidney Street siege of 1911 in a terse and well-orchestrated shoot-out which is vastly preferable to Ms Day and her interminable crooning.
Films de France compares the two in its review, calling Lorre "stunning" and saying,
This American remake is certainly more polished than the 1934 original but lacks the frisson of danger and dark, expressionist tones of that earlier film.