Well that didn’t take long! BBC trails Hollywood-style teaser for the new season of Sherlock the SECOND credits roll for its last ever GBBO after losing the show to Channel 4 

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Sherlock fans were sent into a frenzy last night after the BBC piggybacked on the hype of the Bake Off final to unexpectedly announce that the detective thriller would be returning for a fourth series.

The corporation wasted no time in trying to retain viewers after unveiling a Hollywood-style trailer for Sherlock - while the credits for Bake Off were still rolling.

The teasing promo, which lasted around 90 seconds, showed a black screen with the numbers 01.01.17 – suggesting series four of Sherlock will return on January 1.

Viewers quickly took to Twitter to express their excitement at the return of the show - which is one of the biggest draws for viewers on the BBC.

The fact the Sherlock promo ran just as the last ever Great British Bake Off aired on BBC1 suggests bosses are hoping to retain viewers who may be upset that the baking show is making a £75million move to Channel 4.

The BBC is no doubt worried the 14 million viewers who tuned into Bake Off last night may desert the network after the popular show was sold to C4. It is hoping to retain as many as possible by pushing Sherlock - which draws about nine million.

The teasing promo, which lasted around 90 seconds, showed a black screen with a violin and the the numbers 01.01.17 – suggesting series four of Sherlock will return on January 1

Many fans picked up on the BBC's stunt, with one tweeting: 'Got to hand it to BBC. They know when to air their trailers. #Sherlock' It came after the Sherlock promo ran straight after GBBO

The announcement sent fans into a frenzy and Sherlock was trending on Twitter almost immediately. 

However, many fans picked up on the BBC's clever advertising stunt, with one tweeting: 'Got to hand it to BBC. They know when to air their trailers. #Sherlock'

Another added: 'GBBO is over and Sherlock is coming back and I'm so emotional'.

One said: 'You cannot put a Sherlock trailer after the GBBO final. The British people will die,' while another wrote: '#Sherlock when you were going to sleep but then you saw the announcement.' 

Other fans could not contain their excitement, including Twitter user Chris who said season four of the show would 'hit him harder than puberty'. 

Viewers had barely recovered from the Great British Bake Off final when the BBC stunned fans by announcing a date for the new season of Sherlock

The teaser, featuring Benedict Cumberbatch as the contemporary adaptation of Sir Arthur Conan Doyle's Sherlock Holmes, gave glimpses of upcoming scenes with the mysterious lines: 'Everything they know will be tested...Everyone they know is under threat.'

It comes just a day after Cumberbatch himself hinted that the next series will be so dramatic fans might require a break from the show afterwards.

But the British star, 40, revealed there could be a longer gap than normal between instalments after the forthcoming episodes. 

Everything Sherlock fans know will be 'tested' as the detective thriller series returns to screens at the beginning of next year

He said on Tuesday: 'I think there will be a lull. I don't think it will be in a year and a half necessarily but we will wait and see and maybe it will be.

'First and foremost we have got a fourth series for people to watch and understand and when they watch it they might go 'Oh yeah, maybe there does need to be a break now' because of what happens in it. No spoilers!'

However, Cumberbatch was adamant that his new role as superhero Doctor Strange in Marvel's new film of the same name will not impact on his future in Sherlock.

He said: 'Let me put that one straight, that is nothing to do with this.

'They moved the schedule to accommodate Sherlock, there is a lot of mutual love between those two enterprises and there is no reason why one cancels out the other.'

The comic book giant was so keen to cast Cumberbatch in the blockbuster movie they shifted the filming schedule and release date, he said.

'You have a lot of responsibility, especially to them, because in this instance they did something they had never done before because I was doing Hamlet (at The Barbican in London) and that is when they wanted to film after offering me the role and I had to turn it down. 

The teaser, featuring Benedict Cumberbatch as the contemporary adaptation of Sir Arthur Conan Doyle's Sherlock Holmes, gave glimpses of upcoming scenes with the mysterious lines: 'Everything they know will be tested...Everyone they know is under threat.'

'They went to other places with the part but kept coming back to me and eventually went 'Oh all right, we will change our filming schedule and release date' which is a huge, huge honour.'

Speaking about series four of Sherlock, Cumberbatch said: 'We'll see how this series lands. It's been great fun to come back and do it. How it will continue in the future, who knows?'

Cumberbatch had sparked fears that he'll soon be quitting as Sherlock Holmes by saying 'it's a painful thing to say, but maybe series four is it.'

Yet the actor has helped put fans' minds at ease by insisting that there could still be a fifth series of the iconic TV show.

Speaking on BBC Radio 2, the 40-year-old actor clarified his words, putting the rumour to bed. 

Speaking about series four, Cumberbatch said at the time: 'We'll see how this series lands. It's been great fun to come back and do it. How it will continue in the future, who knows?'

When asked if there will be another series of Sherlock, Cumberbatch said: 'Yes. Listen I know where this [rumour] came from.

Benedict Cumberbatch had sparked fears that he'll soon be quitting as Sherlock Holmes by saying 'it's a painful thing to say, but maybe series four is it.'

'This came from an arts desk or any kind of news outlet going, 'oh we really need a story', so they sort of shipped out this quote which said that I said, 'this is the last one', which is not what I said.

'I said, 'for the time being'. And you'll see when you watch [the new series], that there's a good reason why I said that.

'We won't be doing one immediately after this one airs. That's all I meant. We never ever say never on that show. We love doing it.'

'There might come a time [when the show ends], or there might come a time when there's a big gap. That's a possibility,' said Benedict.

When asked if there will be another series of Sherlock, Benedict said: 'Yes. Listen I know where this [rumour] came from.'

'I suppose [it could end] but I never say never. I enjoy him too much. I enjoy the show too much and the people in it.'

'I can't wait, having read the scripts. They are the most amazing reads,' he said. 'I think this series is going to be the best.'