Alan was broad, strongly built and tall, with a square, determined jaw and unruly brown hair. His deep-set, clear blue eyes were his most remarkable feature. The short, slightly retroussé nose and humorous lines of his mouth gave him a youthful – sometimes a childlike – appearance. So much so that in his late thirties he was still at times mistaken for an undergraduate; hence occasional attempts were made to “prog” him.

In dress and habits he tended to be slovenly. His hair was usually too long, with an overhanging lock which he would toss back with a jerk of his head. The first thing to be done when he came home was to send him to have his hair cut. When he did take the trouble to comb it, five minutes later he would run his fingers through it so that once more it would be standing on end. At King's, for a time he took more trouble with his clothes and even subdued his hair. But when the war came he was seldom at home, clothing and sartorial advice were both rationed, and he relapsed into the old ways. In his last years there was again some slight improvement and he used to object to complaints about his clothes. The real trouble, perhaps, was not so much the clothes that he wore as the way in which he wore them.