Tom Hiddleston plays Sherlock’s brother in a brand new trailer released by the BBC.

But before fans get too excited, it seems that the clip is just a mock-up following rumours that the British heartthrob was set to star in Season 4.

Playing on every fan’s fantasy, the new clip cleverly promotes both Sherlock and The Night Manager on the BBC Store Twitter account.

The tagline on the trailer reads: “Blud” rumours are flying - but what could #Hiddlebatch actually look like? Watch this...”

Leaving fans even more confused than they were, the clip predictably sent Twitter into meltdown.

“Pls don't prolong our agony and just get Tom to play the third Holmes brother already,” wrote one person.

Another posted: “Do not toy with my like this. Do not get my hopes up for nothing, please. I can't handle this.”

The rumour mill started spinning when the cast of Sherlock appeared at Comic Con to launch the trailer for Season 4 last weekend.

Cumberbatch hinted that they were set to introduce his secret brother Sherrinford during the convention, with many speculating that Hiddleston could be set to take on the role.

Series co-creator Mark Gatiss fuelled the flames of speculation later in the week by posting a snap of Hiddleston with the cast.

The real BBC trailer for the forthcoming season was released over the weekend, hinting that this could be the ‘darkest’ series yet.

While the one-and-a-half minute clip doesn't give much away in regard to storylines, it does reveal that all the main cast will be returning and gives a first look at newcomers including Toby Jones.