Some viewers will recoil from the very idea of BBC1 updating Conan Doyle's characters to modern London, with [...] a Dr Watson who fought in Afghanistan.
From Wikipedia, on Conan Doyle's Watson:
In the debut Holmes story A Study in Scarlet (published in 1888), Watson, as the narrator, tells us that he had received his medical degree from the University of London in 1878, and had subsequently gone for training as an Army surgeon. He then joined British forces in India, saw service in Afghanistan...
So, in fact, not an update at all. Sigh.