A Change of Heir — Michael Innes

George Gadberry, 'resting actor', packs his bags and heads for obscurity when the Tax Inspector beckons. Then he receives a mysterious invitation and a proposition that could lead to enormous riches. Wealthy imbiber, Nicholas Comberford, wants George to impersonate him in order to secure a place in the will of fabulously affluent Great-Aunt Prudence, who lives in a Cistercian monastery and won't allow a single drop of liquor in the place. Gadberry's luck seems to have changed - but at what cost?