imagined age progression of Andrew Gosden as he might look now

A desperate search for a missing teenager with family in Chislehurst and Sidcup has been given a boost with the offer of a Porsche for information to help find out what has happened to him.

Andrew Gosden who went missing Sept 14 2007 has a distinctive double ridge on his ear. He's from Doncaster and has family links with Chislehurst and Sidcup

It is five years since gifted mathematician Andrew Gosden, then 14, stepped off a train at Kings Cross, having travelled down from his home in Doncaster and seemingly “disappeared in to thin air”.

The teenager has strong family ties to the Chislehurst and Sidcup areas and had visited them on family holidays.

His aunt, Linda Gibbens, lives in Chislehurst and his uncle Michael and grandparents Ray and Val Gosden live in Sidcup.

Another aunt Chrissie Gosden, who also lives in Sidcup, has been selected to carry the Olympic torch in Bexley because of her involvement in guiding.

They have all helped in the search for Andrew and handed out leaflets at a Muse concert at The O2 and supported his family, dad Kevin, 46, mum Glenys, 47, and 20-year-old sister Charlotte.

Andrew also has a distinctive double ridge on the side of his right ear.

Their friend, Kent businessman Barry Ford, has decided to offer his sports car in a bid to find out what has happened to the teenager – who is now 18.

Mr Ford said: “In the very earliest stages I had hoped a reward scheme would assist, and to put a slight twist on this I have decided to offer my car as an incentive free of charge to anyone who can offer Kevin and Glen information which will determine Andrew’s location.

“I still firmly feel that this situation will be resolved and the answer will be found, either by accident or by design, no matter I am sure you will agree we will accept it from any source at any time.”

Mr Gosden said: “I can’t ever express the gratitude that someone is prepared to do that for you.”

The family have struggled to come up with a reason why Andrew would disappear. There has even been a sonar scanner search of the River Thames for the boy.

Mr Gosden said: “We have got no idea at all what made him walk out of the door that morning – absolutely none.

“In a way it would be easier if we could put it down to something.”

In a message on their website his family said: “If you should ever read this, forget about any water under the bridge and please have no fear about making contact with us.

“We do not care where you have been or what lifestyle you choose for yourself. We only want to know that you are safe and well and to help and support you if we can.”

Anyone with information on his whereabouts should contact Missing on 116000 or contact www.helpustofindandrew.weebly.com