Murder victim Alexandra Morgan feared she may be harmed so left 'box of clues' to help catch killer

• ITV Meridian's John Ryall looks back at how an evidence trail left by one of Mark Brown's victims triggered a huge joint operation by Kent and Sussex Police

It was a case that started as a missing person inquiry and developed into the highly complex investigation of a horrifying double murder.

The victims - two mothers in their mid-30s with strikingly similar looks.

Alex Morgan, 34, was the first of the two women to come to police attention. In November last year, she left her two children with relatives, saying she was going away for a few days. When she didn't return, she was reported missing.

At her last known location - a garage close to her home in Sissinghurst, Kent - police discovered CCTV footage of her buying petrol. 

Her mobile phone trail, examination of CCTV from more than 100 rural locations - and Automatic Number Plate Recognition records - tracked her driving her white Mini Cooper 18 miles to Little Bridge Farm near Hastings.

And security cameras at the scrapyard opposite captured the most important CCTV evidence of the investigation.

• CCTV footage of Alexandra Morgan buying petrol was considered a key piece of evidence

"That footage was absolutely key," said Libby Clark, of the Crown Prosecution Service.

"At 7.58 on that Sunday morning it clearly showed Alex's car entering the farm along with a second vehicle - a gold Jaguar owned by Mark Brown."

Police checks showed Brown, who rented a yard at the farm, had no criminal record. But detectives discovered that he'd met Alex through an adult services website - and that he'd repeatedly searched the internet for violent sexual content.

He was arrested on suspicion of Alexandra Morgan's murder  -  and a police search was launched at Little Bridge Farm.

They drained a pond the size of half a football pitch, examined a shipping container with bedding and a barn where Brown stored parts and worked on cars.

He told police he wanted to help but did not know what had happened to Alex.

They later searched a building site near Sevenoaks where Brown had worked. Inside an oil drum, they found the remains of an intense fire - and a tooth that matched Alex's dental records.

Confronted with that evidence, Brown changed his story, claiming that Alex had died in a fall on his land and he 'panicked' and disposed of the body by fire.

Police discovered phone messages from Brown offering Alex £100,000 for 'filming work'.  

Alex was excited about the prospect of the money and researched business ventures she could start with the cash. But at the same time - frightened of Brown and fearing for her safety -  she left a 'box of clues' at her home. 

Libby Clark of the CPS said: "She left a note addressed to one of her sons. It said 'Let's go rollerblading.' That was a clue to go to a box under a TV in his bedroom where his rollerblades were kept.

"In that box there was £2,000 in cash - a significant sum for Alex - and there was a note we've called something of a 'breadcrumb trail'.

"There was a mobile phone and a PIN number.

"There was also the postcode of Little Bridge Farm." 

As the hunt for clues continued at the farm, police also searched Brown's work van. Inside it, they found medication in the name of Leah Ware. 

They then discovered that she too was missing, that she too had visited at Little Bridge Farm - and that it was her last known location.

Witness by witness, police built up a picture of his two-year relationship with Leah, who had disappeared six months before Alex.

She was a sex worker he'd met through the same website that led him to Alex.  

A mother of three children, she was on medication for mental illness. She used heroin and crack-cocaine and lived a chaotic life, often disappearing for weeks at a time.

For long periods she she lived in Brown's shipping container at Little Bridge Farm. He helped her out with money from time to time.  But - say prosecutors - in reality she was his prisoner.

"There was a bed in there - it was made up to look like a bedroom," Ms Clark added. "But it must have been very frightening to be there alone at night and we know from witnesses that in reality Leah was locked in."

• Libby Clark from the Crown Prosecution Service

After her disappearance, Brown continued to collect her medication and draw money on her cashcard. Her body has never been found - and exhaustive checks for proof of life have led nowhere. 

Brown told the jury 'I never hurt a hair on her head'. But police are certain he killed her and probably disposed of her body - like Alex's - by fire

At his trial Mark Brown, who's 41, was asked how long he'd been using adult services websites like the one through which he met Alexandra Morgan and Leah Ware. 

"Since the age of 18 or 19," he replied.

So were Alex and Leah his only victims?

Police say they have no evidence of any others.

But they want to hear from anyone with information that may link Brown to any unresolved missing persons inquiries - or unsolved murders.