Some eagle-eyed Stateside Sherlock fans may have solved the mystery of the red letters as long ago as January, but those of us who watched in the UK could still be unaware that there was a secret Doctor Who message contained in the US credits of series three opener The Empty Hearse…
PBS’s Masterpiece Mystery strand – which features a range of British detective series also including Poirot, Endeavour and Miss Marple – adds its own branded credits to the end of the shows.
That gave Sherlock co-creators and Doctor Who writers Mark Gatiss and Steven Moffat the chance to tamper with them, picking out certain letters in red to spell out “Weng-Chiang” – the name of the eponymous evil god in classic 1977 Who episode The Talons of Weng-Chiang.
But what made the pair choose this story? Well, it’s the only adventure in which Tom Baker’s fourth Doctor is seen without his trademark scarf, instead wearing an outfit unmistakably reminiscent of Sherlock Holmes – deerstalker and all.
Here’s a handy video to help explain it to you in more detail…
Sign up to the Radio Times newsletter for the latest TV and entertainment news