Before Sherlock was reworked for broadcast, each episode had originally been planned to run for 60 minutes.
The original pilot, later known as the unaired “A Study in Pink,” was filmed in that format. After reviewing it, the BBC decided that the series should consist of longer episodes, commissioning three approximately 90-minute instalments for the first series instead.
The pilot was not simply extended with extra scenes. It was substantially rewritten and reshot, with Paul McGuigan directing the broadcast version rather than Coky Giedroyc, who directed the original pilot. The resulting broadcast episode had an approximately 88-minute running time and premiered on BBC One on 25 July 2010.
The change helped establish Sherlock’s distinctive format: feature-length mysteries with room for layered deductions, character drama, and several plot turns. The planned 60-minute length is therefore easy to confuse with the later broadcast runtime, especially because the unaired pilot survives as a DVD extra.