Watch The Vamps sing a capella in exclusive clip from Cat Deeley's new Sky singing show

In brand new Sky 1 show Sing: Ultimate A Cappella, it's not just the competing groups who have to perform entirely without a band or backing track.

The guest performers who feature on the show each week also have to sing totally naked (only vocally, thank goodness); first up to the challenge are boyband The Vamps.

Here's an exclusive clip from the first episode of the show, with the band performing their single Middle Of The Night alongside the show's house band The Sons of Pitches.

The brand new singing competition hosted by Cat Deeley sees 30 of the UK's best a cappella performers competing for the chance to record an album and release a single in time for Christmas.

The competition is fierce and the standard is high, as you can see from this clip of choir Semi Toned performing in episode one:

"There are no musical instruments, no backing tracks," Cat told RadioTimes.com. "There really is nowhere for anybody to hide."

Sing: Ultimate A Cappella airs 9pm on Friday 6th October on Sky 1