Andrew was 14-years-old when he skipped school, withdrew £200 from his bank account and bought a one-way train ticket to London, on September 14 in 2007.

The teenager, who lived in the Balby area of Doncaster, was last seen at London King’s Cross on CCTV footage, at around 11.20am that day.

His family still do not know what happened to him or why he travelled to the capital.

Andrew Gosden was 14-years-old when he skipped school, withdrew £200 from his bank account and bought a one-way train ticket to London, on September 14 in 2007.

Kevin Gosden, 56, said he still holds out some hope that he will see his son again, adding: “If you let go of that, you just have to give up completely”.

He said “The most difficult thing to deal with is the not knowing, but then the possibility that you might find out something concrete is a little bit torturous.

“And of course there's an element of fearing what you could find out.”

He added: “It's impossible to describe. It is just horrible. After 15 years, we're still pretty much in the same place.

"He's now been missing a year longer than we had him in our lives, which is quite a difficult landmark.

“It's not like losing a loved one, when you know that they've passed away and it takes time but you get through it.

“Whereas we’re stuck endlessly puzzling, wondering, searching and hoping. Just going round and round in circles.”

South Yorkshire Police has not managed to track Andrew down and there have been no confirmed sightings of him since he was reported missing.

But officers investigating the disappearance did make two arrests in London, December.

A 45-year-old man was arrested on suspicion of kidnap, human trafficking and the possession of indecent images of children.

A 38-year-old man was also arrested on suspicion of kidnap and human trafficking.

Both of the men were then released under investigation while enquiries continue.

Mr Gosden said it has been a “particularly intense” year and he is still waiting for police to provide an update on the investigation.

South Yorkshire is appealing for information about Andrew’s whereabouts and the force has issued a series of age progression images, depicting what Andrew could look like today, as a 29-year-old man.

Andrew had a distinctive right ear and required glasses when he left home in 2007. He was also deaf in his left ear.

Anyone who had information which could assist the investigation should contact South Yorkshire Police on 101.

And anyone affected by a disappearance can contact the Missing People helpline for support and advice, on 116 000.

Andrew Gosden's father 'can’t afford to lose' hope 15 years after he disappeared