Described as “a modern day urban thriller” the episode is the first to show fans the version of Clara Oswald (Jenna-Louise Coleman) who will accompany the Doctor across the series’ eight adventures.
The actress has already appeared in two stories, with her character dying at he end of each.
Set in London against the backdrop of new and old iconic landmarks, The Shard and Westminster Bridge, ‘The Bells of St John’ will also establish a new nemesis, the Spoonheads, who will battle the Doctor as he discovers something sinister is lurking in the Wi-Fi.
Steven Moffat, executive producer and lead writer, said: “It’s the 50th year of Doctor Who and look what’s going on! We’re up in the sky and under the sea! We’re running round the rings of an alien world and then a haunted house.
“There’s new Cybermen, new Ice Warriors and a never before attempted journey to the centre of the TARDIS. And in the finale, the Doctor’s greatest secret will at last be revealed! If this wasn’t already our most exciting year it would be anyway!”