British poet and novelist Helen Dunmore has posthumously won the 2017 Costa Book of the Year prize for Inside The Wave, her 10th and final poetry book.

Dunmore, who died of cancer in June last year aged 64, previously won the Poetry Award for the collection, which explores the borderline between the living and the dead.

The judges described Inside The Wave as “an astonishing set of poems – a final, great achievement”.

She has become the second writer in the award’s 46-year history to win the overall prize posthumously – Ted Hughes previously won the Poetry Award and Book of the Year in 1998 for Birthday Letters.

Inside The Wave is the eighth poetry collection to take the overall prize at the Costa Book Awards.

Dunmore beat Gail Honeyman’s Eleanor Oliphant Is Completely Fine, the bookies’ favourite, to the accolade.

The other nominees in the running for Costa Book of the Year were In The Days Of Rain by Rebecca Stott, Reservoir 13 by Jon McGregor and Katherine Rundell’s The Explorer.

Dunmore’s son Patrick collected the prize – a cheque for £30,000 – at an awards ceremony in London on Tuesday.

Wendy Holden, chair of the final judges, said of Inside The Wave: “We all felt this is a modern classic; a fantastic collection, life affirming and uplifting.

“The poems carry powerful messages that speak to all of us.”

Luan Goldie, a primary school teacher and former business journalist, topped a public vote to be named the winner of the Costa Short Story Award for her story Two Steak Bakes And Two Chelsea Buns.

She was awarded £3,500, while two runners-up, civil servant Chris Hunter and poet Frances Ainslie received £1,000 and £500 respectively.