Writer defends reboot from accusations of self-indulgence, saying it is not a detective show but 'a show about a detective' Please note: this article contains very mild spoilers on the final episode of the current series

This article is more than 6 years old

This article is more than 6 years old

Sherlock will be back for a fourth series on BBC television, its executive producer Steven Moffat has revealed at a preview of the third episode, The Last Vow.

Centred around a blackmail, the final episode of the third series will be broadcast on Sunday.

Moffat brushed aside the views of some critics and viewers who found the opening episode, The Empty Hearse, too self-referential as it ran through the ways in which Sherlock might have escaped what seemed like certain death in his fall from the roof at the end of the previous series.

Moffat said: "It has had a brilliant response. I read the press, it is not true".

"It is not a detective show. It is a show about a detective … It is a show that celebrates a clever man. So we make the show look complex."

Steven Moffat. Photograph: Ian West/PA

The final episode blows away the semblance of Dr Watson's retreat into a semi-conventional happy, married life with his pregnant partner Mary, which was the centrepiece of last Sunday's The Sign of Three.

Sherlock – who appears to have found a girlfriend – is facing mortal danger once again, but this time at the hands of a new villain, Charles August Magnussen, played by The Killing's Danish actor Lars Mikkelsen.

A newspaper proprietor with some very unpleasant personal habits – he urinates in Sherlock's fireplace– Magnussen is the one man Sherlock truly hates.

Sherlock says: "I've dealt with murderers, psychopaths. None of them can turn my stomach like Charles Augustus Magnussen."

We also catch our first sighting of Sherlock in a crackhouse – a reference to the original detective's use of drugs – which Watson visits to find a neighbour's son.

Moffat said: "He is completely human. He has emotions but he suppresses them to be a better detective. He believes emotion gets in the way of his brilliant brain."

The next series scripts are already being planned: "We have got plans, they tend to be what exciting twists and turns we can have. Not blowing up the world" he said.

Moffat also added that he saw no point in making a Sherlock movie when he could create three feature-length new episodes, which can be shown in the cinema on release.

Perhaps Sherlock's Lazarus-style return to life may be catching. Though Magnussen appears to be a one-episode character, Moffatt did not rule out bringing him back. Which also left open the question of whether Moriarty, played to perfection by Andrew Scott, really is no more.