Prime Minister David Cameron gave his mother Kerry, 39, fresh hope when he lent support for a new investigation.

No trace of the 21 month old was ever found after he vanished from Kos on a family holiday in 1991.

Mystery disappearance: Ben Needham was just 21 months when he was seized in Kos, right. Left is a computer generated image of what he might look like now

Kerry, 39, believes that her son was abducted and then sold for adoption. Now South Yorkshire Police could be called in to investigate the two decade old bungled probe.

The mother is also calling for Greek police to re-open the investigation as Mr Cameron signaled to her in a letter that British police could investigate.

Kerry told the Sunday Express: 'I have written to every Prime Minister since Ben went missing and have received run of the mill replies.

'Mr Cameron's response seems the most sincere. His letter felt like he really sympathises me.'

Kerry last visited the popular tourist island in 2008 ? but has no intention of going back after being rebuffed by the authorities.

Mr Cameron wrote to her: 'I can promise you that South Yorkshire Police will have the support of the government and our embassy in Greece in pressing for whatever information or co-operation they require.'

A new artists impression of what Ben might look like has been released today that shows what he might look like.

Kerry will mark the 20th anniversary of the disappearance on July 24 this year.

Ben and his mother were staying with his maternal grandparents Eddie and Christine Needham in Iraklise, Kos, when he disappeared.

The toddler was seized within moments of him going to play outside a farmhouse, which his grandfather was renovating in the village of Iraklise.

Kerry was working as a waitress on the island at the time.

She has a 17-year-old daughter Leigh-Anna and married Craig Grist in 2006.