Caroline Glachan's body was found dumped face down in a river, her head smashed open. It was later revealed that she was still alive when put in the water. Her killer still roams free today.

Trevor Deely vanished from the streets of Dublin in December 2000. His disappearance was the subject of a high-profile search and publicity campaign, but no trace was ever found.

Penny Bell was stabbed 50 times in the chest and arms. Nobody has ever been convicted of her murder. She had withdrawn £8,500 from her bank the day before, which was never found.

Valerie Graves was murdered with a claw hammer whilst house-sitting a £1.6 million property. Police do not believe that Valerie knew her killer.

Barry Rubery returned home in 2010 after an evening out. The next day, he was found with fatal head injuries, face down in a pool of blood.

Claudia Lawrence was reported missing in 2009. She has not been heard from since. No body has been found, and no one has been brought to trial.

Annie McCarrick vanished in 1993 after being seen with an unidentified man. No trace of her has ever been found, despite her father's frustration at the Police's attempts to find her.

In 1992, a lorry driver discovered the body of Natalie Jane Pearman in a lay-by in Norfolk. Forensic swabs revealed semen present in her body, but this has never been matched to a suspect.

Alan Wood was tortured at his home, his bankcards stolen and used over the following days. It is not known why the most disturbing crime in Lincolnshire in recent history was committed.

Daniel Entwistle vanished from his hometown of Great Yarmouth, and has never been found. Now, new evidence has emerged that might move the investigation on.