Dr Watson considered Holmes to be "the worst tenant in London', who 'keeps his cigars in the coal-scuttle, his tobacco in the toe-end of a Persian slipper, and his letters transfixed by a jack-knife to the centre of the wooden mantelpiece". Strange visitors, chemical experiments and late-night violin playing also tried the patience of their landlady Mrs Hudson.

He was however the great detective's loyal companion and Holmes was aware of his value - he said to him on one occasion: "it may be that you are not yourself luminous, but you are a conductor of light".