Rotary GS02424/21 - Benedict Cumberbatch - Sherlock Holmes
The watch can be clearly seen in episode 2 of the second season, "The Hounds Of Baskerville", when Sherlock enters the secure military site (about 24m35sec into the episode) and checks his watch to see how much time he has left.
The watch has a steel case, silver dial with one subdials, roman numerals, black leather strap. This is a quite affordable watch, with a retail price of £99 (approx. $150 or €120). The design of the watch is very similar to the high-end Breguet Classique watch.
Unfortunately the Rotary GS02424/21 is not produced anymore. UPDATE the watch has been re-issued by Rotary and is now know as the Sherlock watch, see it on the Rotary website, find it on eBay or buy it for only £84 on Amazon.co.uk.