Festival No 6 2015 line-up: James to headline Sunday night alongside Grace Jones

Band join already confirmed headliners Metronomy and Belle & Sebastian

Mancunian indie rockers James (Press Handout)

Mancunian rockers James have been announced as surprise headliners for Festival No 6.

The band will co-headline the festival’s main stage on Sunday 6 September with Grace Jones.

The indie rock band will join fellow Festival No 6 headliners Belle & Sebastian, who will top the bill on Saturday, and Metronomy, who will perform on Friday.

James have been on the road following the critical acclaim of their latest album La Petite Mort last year, playing their classic Nineties songs as well as new material.

Aerial views overlooking Portmeirion village during Festival No 6

They join a line-up that includes Catfish & The Bottlemen, James Bay, Years & Years, Badly Drawn Boy and Mercury Prize nominee Kate Tempest.

Other new additions to the festival line-up include New York hip hop producer Arthur Baker and the return of composer-in-residence Joe Dudell, who will be collaborating with Gaz Coombes, Edwyn Collins, Jane Weaver and Rae Morris on new material.

Festival No 6 in full swing in Portmeirion village (Getty Images)

Set in the picturesque Italiante village of Portmeirion in north Wales, the boutique festival offers a broad arts and music programme including talks from Irvine Welsh, Maxine Peake and Dom Joly.

More music acts, venues and famous chefs will be revealed later this summer.

Festival No 6 takes place in Portmeirion from 3-6 September. www.festivalnumber6.com.