Presenter Laura Ansell introduces the first episode of her BBC Sounds series DNA Trail: The Promise.

Billy from Brighton is in his 30s when he’s told by his mum Madeleine that the man who brought him up wasn't his ‘real’ dad.

Armed with only his name: William Anderson and the fact he served in the Royal New Zealand Air Force, Billy goes in search of his biological father. He tracks him down in the late 1970s but is rejected.

On his deathbed in 2006, Billy's then teenage daughter Laura and his wife Jayne make him a promise - to find Billy’s family and get a photo of his dad - something that Billy longed for his whole life.

To listen to the rest of the series just search for DNA Trail on BBC Sounds.