Sherlock fans were left outraged when the BBC’s latest Sunday night drama turned out not to be a secret fourth episode of their favourite show.

The third and final instalment of Sherlock Series 4 aired last Sunday, January 15, with no indication of the show might be back, and was replaced in the 9pm slot by Apple Tree Yard.

The new drama is based Louise Doughty’s thriller novel about a middle-aged woman who begins an affair that spirals out of control.

Some Sherlock fans were convinced that, in keeping with the show’s tricksy nature, Apple Tree Yard was actually a code name for an extra episode of Mark Gatiss and Steven Moffat’s present-day mysteries.

Apple Tree Yard, BBC1 - in pictures 8 show all Apple Tree Yard, BBC1 - in pictures 1/8 Emily Watson as Yvonne Carmichael BBC/Kudos/Nick Briggs 2/8 Ben Chaplin as Costley BBC/Kudos/Nick Briggs 3/8 Mark Bonner as Gary Carmichael BBC/Kudos/Nick Briggs 4/8 Steven Elder as George Selway BBC/Kudos/Nick Briggs 5/8 Assad Zaman as Sathnam BBC/Kudos/Colin Hutton 6/8 Susan Lynch as Susannah BBC/Kudos/Nick Briggs 7/8 Olivia Vinall as Carrie BBC/Kudos/Colin Hutton 8/8 Jack Hamilton as Adam BBC/Kudos/Colin Hutton 1/8 Emily Watson as Yvonne Carmichael BBC/Kudos/Nick Briggs 2/8 Ben Chaplin as Costley BBC/Kudos/Nick Briggs 3/8 Mark Bonner as Gary Carmichael BBC/Kudos/Nick Briggs 4/8 Steven Elder as George Selway BBC/Kudos/Nick Briggs 5/8 Assad Zaman as Sathnam BBC/Kudos/Colin Hutton 6/8 Susan Lynch as Susannah BBC/Kudos/Nick Briggs 7/8 Olivia Vinall as Carrie BBC/Kudos/Colin Hutton 8/8 Jack Hamilton as Adam BBC/Kudos/Colin Hutton

When that turned out not to be the case, social media was rife with unimpressed fans venting their frustrations.

One wrote that it was "absolutely appauling" [sic], while another lamented: "All we wanted was Sherlock..."

It is currently unknown if Sherlock will return for Series 5, with Moffat saying it’s ‘possible’ that the show might be finished.

“If this was the last time – we’re not planning it, but it might be, it’s possible – we could end it [at Series 4],” he told the Radio Times.

“We couldn’t have ended it on any of the previous series because they always ended up with whopping great cliffhangers.”

Apple Tree Yard is set to continue for three more episodes airing on Sunday nights on BBC One.

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