A Matter of WHO is a 1961 British comedy thriller film directed by Don Chaffey and starring Terry-Thomas, Julie Alexander, Sonja Ziemann, Alex Nicol, Richard Briers, Honor Blackman and Carol White.

Aboard an airliner flying from Nice to London, an oil driller returning from the Middle East named Cooper becomes very ill.

[3] The Monthly Film Bulletin wrote: "This latest attempt to emulate Hitchcock never finds a balance between Terry-Thomas's brand of civil service comedy and the surrounding atmosphere of suspicion and peripatetic detection.

The mood aimed at is closest to Hitchcock's Secret Agent [1936]; the actual measure of achievement falls far short.

As it is, a confused script and Don Chaffey's flat direction combine to produce a jaded impression of a number of TV's Interpol episodes running one into another; and Terry-Thomas's none too humorous skirmishing round the haystack ends up forcing from it nothing more deadly than a field-mouse.