How do you find a killer from the past, a murderer who could be anywhere on the planet?

On a heart-breaking anniversary, Julie McKay makes an appeal closer to home.

And you're either going to solve one of the greatest undetected crimes of the century,

or you're going to know that your friend relative whoever is not a murderer and you can

sleep safely in your bad at night. And what leads Gary Mason to a car park and who is this man

walking over for a swab? Could the team and justice be closing in on the killer of Melanie Road?

I'd had walked 36 years in the job at that stage,

and I would have thought that I would have picked up a sense of something,

and I didn't pick up any sense of nervousness more than anyone else.

On a day in June 2014, a 79-year-old woman sat down and wrote a letter.

It was a letter from the heart.

For three decades, Jean Road had held a dignified silence about the murder of her daughter, Melanie.

Karin, Melanie's elder sister, wrote a letter too.

This was not private correspondence.

Instead, it would be put on billboards, published in newspapers and shown on TV.

It was an appeal to people's hearts.

Good evening. The mother of a murdered teenager has written a letter

begging the people of Bath to search their memories to help find the killer.

17-year-old Melanie Road was stabbed to death 30 years ago.

Her mother, Jean, says the crime has torn the family apart.

My name is Robert Murphy. I'm an ITV news correspondent,

and this was when I started covering

...