Please describe John Douglas in the Valley of Fear.

From the text:

Douglas was a remarkable man, both in character and in person. In age he may have been about fifty, with a strong-jawed, rugged face, a grizzling moustache, peculiarly keen gray eyes, and a wiry, vigorous figure which had lost nothing of the strength and activity of youth. He was cheery and genial to all, but somewhat offhand in his manners, giving the impression that he had seen life in social strata on some far lower horizon than the county society of Sussex.