Some are saying that Quartermaine’s Terms was and still is the best play by Simon Gray, whose compulsive smoking and drinking finally killed him yesterday in London, at age 71. But I always had a thing for Otherwise Engaged, a very sharp and funny character study of a British publisher that I saw twice on the Manhattan stage in the mid ’70s — once with original star Alan Bates, and then with Dick Cavett, who wasn’t half bad.