The father of a gifted teenager who vanished exactly a year ago has spoken of his family's desperate need for "closure".
Kevin Gosden, 42, said the baffling disappearance of his son Andrew, of Doncaster, South Yorkshire, had left a huge gap in his family's life.
He spoke as dozens of Andrew's school friends and relatives marked the anniversary with a moving church service in London, where he was last seen on September 14 2007.
The youngster, who would have turned 15 in July, went missing after failing to turn up at school in his home town before boarding a train to London with just £200 from his bank account.
Apart from CCTV footage showing him leaving the capital's King's Cross station later the same day, there has been no firm trace of his whereabouts perplexing police and family alike.
Mr Gosden, who joined his wife Glenys, 44, in laying flowers at the scene where their son was last spotted, said the anniversary marked a watershed in their search.
He said: "This is our final big push to find Andrew. Not to say that we actually will never do anything else but we feel that he may have changed in appearance. In some respects we also need to get a bit of closure for ourselves by saying 'we have done our best for you son'.
"There is a really big gap in our family life. We still love him and we still care about and would just like to know at the very least that he is alive and ok."
Three coachloads of volunteers from Doncaster, including school teachers, pupils and relatives, arrived in the capital to mark the occasion. Wearing yellow t-shirts and pictures of Andrew, they distributed hundreds of posters and leaflets around central London in a bid to trigger the memory that might find the schoolboy.
They then filled St James's church in Piccadilly where a procession of schoolchildren carried a candle for around 30 missing children, including Madeleine McCann. Each read out the name, age and location where the children have disappeared before Mr and Mrs Gosden, and Andrew's 17-year-old sister Charlotte, did the same.