THE teenager who murdered a Scots dinner lady and her young daughter shocked hardened detectives with his calmness as he recounted the killings.

Lucas Markham plotted with his girlfriend Kim Edwards to kill her mother and younger sister in what became known as the Twilight Killings.

The pair – both 14 at the time – bathed together, had sex and then watched several of the popular Twilight vampire movies after murdering Edinburgh-born Elizabeth Edwards, 49, and 13-year-old Katie in their beds.

Believed to be the UK’s youngest double murderers and likened to Bonnie and Clyde during their trial, footage of Markham describing the killings in detail were due to be made public for the first time last night.

In the police tapes Markham can be heard describing how they walked into Mrs Edwards bedroom, stabbed her viciously several times and then smothered her. He then went into Katie’s bedroom and carried out an identical attack.

HeraldScotland:

The pair planned the killings after Mrs Edwards tried to separate the young couple amid growing resentment towards Katie Edwards who, Kim believed, had been enjoying a great deal more attention from their mother.

In the tapes, Markham also makes clear the murders, at the Edwards family home in Spalding, Lincolnshire in April 2016, had been planned and agreed with Kim.

He said: “I went into her room and stabbed her in the neck while she was asleep and smothered her face with a pillow.

“After I knew she’d gone I went into Katie’s room and I thought I stabbed her but I’m not 100 per cent sure if it was her or the mattress and then I smothered her face with a pillow.”

The recordings were broadcast as part of a Channel 5 show Murdered By My Daughter.

Deputy Superintendent Martin Holvey, who spearheaded the investigation, told how Markham’s lack of remorse or emotion had shocked officers.

He said: “You recount the story to your team and everyone sits there, hardened detectives, and thinks, I can’t believe what you’re hearing.

“Over 30 years as a cop, you look at this case and there’s nothing that rivals it.

“A really brutal, chilling, cold and callous act that was carried out by two children on two defenceless victims.”

The teenagers were convicted of murder and each jailed for a minimum of 20 years in November.

At the time, the pair could not be named for legal reasons but this month the restrictions were lifted by three judges at the court of appeal in London.

At the trial it was heard Mrs Edwards and her daughter were stabbed a total of 10 times in a “cold, calculated and callous” onslaught. It later emerged that Kim Edwards had allowed her boyfriend to climb through a bathroom window to carry out the attacks after he gave a prearranged signal, also guiding him round the property.

At the Court of Appeal it also emerged the pair remained downstairs in the house, watching TV and eating food while the bodies lay upstairs.

It was claimed then they showed no remorse when interviewed by officers.

In the documentary Mrs Edwards’ boyfriend Graham Green compared his partner’s daughter to an infamous serial killer.

He said: “I think she’s another Myra Hindley as far as I’m concerned. She should never, never, never be let out.

“She’s trying to put herself on the map. How do you go about planning to kill your mother and sister? How can you plan that?”