Adrian Michael Rodi, 50, was arrested after police discovered Angela Rider, 51, in the early hours of March 5 this year at a house in Cawood, North Yorkshire.
-> Driver aged just 13 caught behind the wheel during 100mph police chase in YorkshireRodi was due to stand trial for murder but instead pleaded guilty to manslaughter with diminished responsibility, which was accepted by the prosecution.
Wearing a light blue shirt and trousers, Rodi appeared in the dock flanked by three officers at Leeds Crown Court.
He spoke only to confirm his name and was assisted by his barrister when the new plea was given.
The court heard Rodi has been questioned by forensic psychiatrists who concluded his poor mental health had played a part in his actions.
Kama Melly QC, prosecuting, said: "Having considered all reports in respect of Mr Rodi and having had conference with the family of the deceased, it is the view of the crown that a plea of guilty to manslaughter with diminished responsibility is accepted by the Crown."
-> Tributes to 'beautiful' mum found dead at Yorkshire propertyJudge Tom Bayliss QC said Rodi could face life in prison for the killing.
He added: "You have pleaded guilty to manslaughter and I must sentence you.
"In order to determine the sentence that I have to pass, I need to know what the opinion is of the doctors and I'm adjourning for that to be done.
"Sentence will be passed when I have that report."
Rodi will be sentenced on November 12 when a report has been prepared by the doctors.
The community and her family were left rocked by the tragic, sudden death earlier this year.
Ms Rider attended Ladderbanks Middle School in Baildon, and then went on to Rhodesway Upper, in Allerton.
She worked at Yorkshire Building Society before she began a successful career in property developing.
She was mum to Sara, 26, and was lady captain at Rudding Park Golf Club, in Harrogate.
In a joint family statement, Ms Rider's daughter Sara, her mother Wendy Brown and her sister Tracy Mills described her death as a "devastating loss".
"Angela was the most beautiful, fantastic mum, a wonderful daughter and the best sister anyone could have wished for," they said.