A film version of Dion Titheradge's play of the same name, in which a gang of international spies are tracked to a Kentish inn called The Crooked Billet by a retired Scotland Yard detective.
A piece on 'British Talking Pictures' in the London Times indicates that 'The silent films made by the Gainsborough organization in the last year will not be released until they have been converted into talking or part-talking films. On completion of their studios at Islington The Crooked Billet, The City of Play, and Taxi for Two will be converted into talking films, and it is hoped that all of these will be ready for release in the autumn'. (Wednesday 26 June 1929, p.14).
In the case of The Crooked Billet, however, this seems to have been a re-release: the British Film Institute, for example, notes the 1929 release of the silent film.