The hugely-popular programme, starring Benedict Cumberbatch as Sherlock Holmes and Martin Freeman as his sidekick Dr. Watson, is to return for a one-off Christmas special set in Victorian London instead of modern times like the previous three series.

Speaking at Comic-Con 2015 in San Diego, California, co-creator Steven Moffat revealed, "It's still the same sense of humour, it's still very much the show you know... But it's in the 'correct' era, which was unbelievably thrilling."

Moffat also revealed fans will be able to watch the special installment on the big screen.

Cumberbatch and his co-stars Andrew Scott and Mark Gatiss were unable to make it to California for the convention so they filmed a video message to apologise for their absence.