A man hid two knives in his socks and stabbed his wife to death at a derelict mental hospital.
Michael Cowey, 49, lured mum-of-three Gemma to the former site of St Andrew's Hospital in Norwich, Norfolk, on the pretence that he wanted to talk to her.
However, an argument began when he confronted her about relationship issues.
When interviewed by police, Cowey told officers that he took the blades that were hidden in his socks and stabbed her more than 20 times in her back and neck. He then ran from the scene.
The devoted mum was found with serious injuries by members of the public in the old hospital mortuary.
Emergency services including an air ambulance were called, but despite the best efforts of paramedics she was pronounced dead at the scene on June 19, this year.
Cowey was arrested by police three hours later, 120 miles away in Warwickshire, and was taken to a police station in Norfolk to be questioned.
A post mortem examination found Gemma had died as a result of stab wounds.
Cowey appeared at Norwich Crown Court on Friday, November 5, and pleaded guilty to her murder, as well as to the possession of two knives.
He had previously been deemed unfit to enter pleas, but a psychiatric report eventually concluded he was able to do so. He will be sentenced by a high court judge on December 11.
Gemma's mum, Lina Smith, was in court for the hearing and said that "no sentence will ever be enough".
“We, Gemma’s family, state that today’s guilty plea hearing in the Norwich Crown Court is the outcome that we were hoping for. We are now gearing up for the maximum sentence possible which will go some way to help us with the horror of what happened to our Gemma. No sentence will ever be enough", she said.
Gemma, who was also known as Gemma Lynne Marjoram, was described as a "devoted mummy" and "loving big sister".
An earlier family statement said: “Our beautiful girl, Gemma Lynne Marjoram, was cruelly taken from our lives on Friday, June 19.
“Gemma, a devoted mummy to three children, Kacie, Callum and Abigail, and loving big sister to Joanne and Kimberley.
“We are beyond heartbroken. We have no more words.”
Det Insp Lewis Craske from the Norfolk and Suffolk Major Investigation Team (MIT) said: “It was a cowardly attack which was planned, by the fact he took two knives to the scene.
“Although Cowey has saved the family the trauma of a trial, his plea has been forced upon him due to the thorough investigation into the circumstances of this offence and his previous relationships.”
Following the customer advisor's death, a crowdfunding appeal was set up to help pay for her funeral, reaching its £5,000 target in just three days. A total of £6,787 was raised through donations.
It was set up by Sophie Baldwin, who was a former schoolfriend of Gemma.
She said: “Thank you for your help and support – we have done a fantastic job in raising this much. Please, please keep sharing.”
St Andrew's Hospital, where Gemma was found, used to be known as the Norfolk County Asylum and dates back to the 19th century.
It closed in 1998 and some of the Grade II listed buildings were converted into homes.
The main building, St Andrews House, was used as offices until 2007 and put up for sale in January 2011.