Unlocking Sherlock is a one-hour special that explores how writers Steven Moffat and Mark Gatiss created the hit television sensation. The special takes viewers on a personal voyage through the versions of Holmes that have served as inspirations for the new series – the original stories, their factual origins, hundreds of film adaptations – to arrive at their thoroughly modern Sherlock. Moffat and Gatiss explain the challenges they encountered adapting the original adventures of the iconic super-sleuth. The special goes behind the scenes on the set of the hit television series, and includes interviews with actors Benedict Cumberbatch, Martin Freeman and Lara Pulver, who talk about the reinvention of their fictional characters.

Sherlock faces his biggest challenge of all - delivering a best man's speech on John's wedding day.