Organisers have added two more acts to the Folk by the Oak festival bill set for Hatfield this summer.

The Unthanks join FBTO's Main Stage line-up while pioneering new Celtic fusion project We Are The Monsters have been announced for the smaller Acorn Stage.

The music festival is set to return to the Queen Elizabeth Oak Field in the grounds of Hatfield House on Sunday, July 17.

Early bird tickets for Folk by the Oak are available until January 31, after which the price rises.

Mercury Music Prize nominated act The Unthanks – featuring Tyneside sisters Rachel and Becky Unthank – join The Proclaimers, folk supergroup Spell Songs, Richard Thompson, and AKA Trio on the 2022 Hatfield bill.

They last appeared at FBTO in 2015 and can count Sherlock and Hobbit actor Martin Freeman, fellow The Office star Mackenzie Crook, the acclaimed Anne and Rules of the Game star Maxine Peake, and Oliver's Army singer Elvis Costello among their celebrity fans.

In fact, recent Unthanks projects include writing soundtracks for Mackenzie Crook’s beautiful adaptation of Worzel Gummidge, and interpretations of the work of female writers ranging from Emily Bronte to Molly Drake and Maxine Peake.

Team FBTO said: "When we first heard BBC Folk Album of the Year, Mount The Air in 2015 we knew we had to book The Unthanks, and their performance at Folk by the Oak that same year was nothing short of incredible.

"Seven years on and we are among legions of folk fans eagerly awaiting the release of their forthcoming new album Sorrows Away, and thrilled that The Unthanks are returning to Folk by the Oak!"

They added: "Expect a performance that showcases new music from Sorrows Away, which as the title suggests promises an uplifting step away from sorrow and into the light, alongside favourites such as Magpie, The King Of Rome, Starless and Mount The Air.

"We simply can’t wait to share this with you!"

FBTO's first Acorn Stage act, We Are The Monsters, brings together members of Monster Ceilidh Band, Kathryn Tickell & The Darkening and The Shee, to form a ground-breaking five-piece electro-folk band marrying traditional roots and electronic influences.

The line-up features accordion star Amy Thatcher, violinist Grace Smith, octave mandolin player Kieran Szifris, drummer Joe Truswell and award-winning electronic experimentalist and bassist David de la Haye.

"Pack your dancing shoes," said Team FBTO. "Their live performance promises to have you up on your feet and raising the roof of our Acorn Stage – we can't wait!"

Ahead of this summer's Folk by the Oak festival, Spell Songs are touring the UK this month.

The acclaimed ensemble brings together the remarkable talents of musicians Karine Polwart, Julie Fowlis, Seckou Keita, Kris Drever, Rachel Newton, Beth Porter and Jim Molyneux plus The Lost Words and The Lost Spells artist Jackie Morris painting live to music.

Visit www.folkbytheoak.com for more on Folk by the Oak.