The BBC has released a preview for the next new episode of 'DOCTOR WHO' to be premiered, the Western-themed 'A Town Called Mercy'.

"The Doctor gets a Stetson (and a gun), and finds himself the reluctant Sheriff of a Western town under siege by a relentless cyborg, who goes by the name of 'the Gunslinger.'

But who is he and what does he want?

The answer seems to lie with the mysterious Kahler-Jex, an alien doctor whose initial appearance is hiding a dark secret.

This season, join the Doctor (MATT SMITH), his companions Amy (KAREN GILLAN) and Rory (ARTHUR DARVILL) - aka the Ponds - and numerous friends on their latest escapades through space and time where they puzzle an unexpected invasion of Earth, save a spaceship full of dinosaurs, don Stetsons in a Wild Wild West adventure and are even kidnapped by the Doctor's oldest foe.

The explosive series concludes with Amy and Rory's heart-breaking farewell - a race against time through the streets of Manhattan. Will the Doctor really lose the Ponds forever? There's only one way to find out..."

Watch the 'A Town Called Mercy' teaser video below...