The Barbary Light — P.H. Newby

As a boy Oscar Hanner tried to run away to Africa, only to end up in Cardiff Docks. Nearly forty years later, as an accountant employed to investigate failing companies, he again feels the need to boldly assert himself, in both his professional and private life. To embezzle part of the funds of the Silent Bottling Company is half of the plan, to make Alex his mistress, the other. But when Sybil, his wife, brings Alex home to live with them it is clear that this particular menage a trois will never work; and the stolen money becomes, in the end, a source of not so much guilt, as embarrassment.