IT’S one of the most popular stage shows in the world – and he is the ethereal lynchpin that holds it all together.

Veteran folk singer Bob Fox is the longest serving Song Man in the hit show War Horse – currently on stage at Mayflower Theatre

Having learnt the guitar at the age of 14, he built a career based on the music of the north - and is now lauded as one of the country’s finest English folk musicians.

From the northeast mining town of Seaham, he started touring in his early twenties, playing folk clubs around the country with songs from pit villages and shipyards.

It’s the magical combination of Bob’s delivery, Song Maker John Tams’ arrangements and the eery tones of the melodian that help give War Horse its gravitas.

Song Man is the invisible observer of the play, appearing at pivotal moments to make time stand still - or move it forward.

Set in WW1, a young farmer’s boy desperately signs up to fight in order to be with his beloved horse Joey. Song Man opens the play with an adaptation of 19th century Bonar and Sankey hymn Only Remembered For What We Have Done.

The lyrics are in honour of those fallen - but are also a reminder of those who committed atrocities in the Great War.

Bob said Tams’ job as Song Maker was to make the songs chosen for the play “very grounded in the English tradition.”

He said: “He took existing songs and tinkered with them to make them relevant. I think that’s why it feels so genuine and so authentic when everybody sings together. The whole idea of Song Man is he is the spirit of the Devon village - he’s not seen by anyone else in the play. He’s making important things happen with these earthy traditional kind of songs. It’s a magical character and a great role to play.”

But Bob’s first job in the theatre was “quite a leap from the song world.” And although he eventually came to love London, being tied to a hit West End show – which has played to seven million people around the world – was a challenge after the folk scene.

But he says all music is folk: “There’s not music except folk music whatever box you want to put it in. If you go back to the times when people came in from the fields and went to the pub they would sing about what they were doing and what went on. Even pop songs for all they’re shallow they’re still folk music because they’ve been written by someone who was making something up. Sometimes they’re very deep and sometimes they’re Agadoo sort of stuff.”

But although the folk scene’s politics have been “diluted” since the 60s and 70s Bob’s audience has stayed with him, and growing up where the only job options were coalmines or the shipyards the tradition is ingrained in him. But he made his escape through music.

“I come from a very working class background. My dad was a coal miner. I escaped because I was musical. You can take the boy out of Seaham Harbour but you can’t take Seaham Harbour out of the boy.

“It’s the same with anyone, it’s the same with Sting who for all those years trying to get away from being from Newcastle has finally come to writing a musical about the shipyards. I got a casting call for it and I would have loved to have been in it but I couldn’t because I was committed to War Horse.”

A Garland for Joey, Bob’s 10th Anniversary Collection of songs from Song Maker John Tams is out now.