A musician wept as he described the moment school teacher Jane Longhurst collapsed dead.
Graham Coutts told how they were having sex in bed as he wound a pair of tights round her neck, something he said heightened the pleasure.
He was on his back while Miss Longhurst was kneeling over him.
He said: "At some point I shut my eyes. The next thing I knew Jane was lying over me and not moving.
"I had already let go of the tights. Nothing made sense. I remember seeing blood."
Coutts, a 35-year-old guitarist and salesman, denies murdering Miss Longhurst and said her death was a tragic accident.
A packed Court One at Lewes Crown Court was hushed on Friday as Coutts told his story and how he had considered killing himself at Beachy Head after Miss Longhurst's death.
Occasionally sniffling, weeping and sipping water, he said Miss Longhurst telephoned his house on the morning of March 14 last year and the pair had agreed to go swimming.
Coutts picked her up in his car from her home in Shaftesbury Road, Brighton, and he said she appeared preoccupied.
They went back to his flat in Waterloo Street, Hove, where he made her tea. Something was bothering Miss Longhurst, 31, and she began crying.
He consoled her on his sofa and they began kissing.
They then moved to the bedroom although Coutts said he had never before thought of Miss Longhurst in a sexual way.
Coutts said Miss Longhurst was unaware he had a fetish for women's necks but she was willing as he caressed her neck.
He put his hand round her throat and he was surprised as Miss Longhurst responded by squeezing the same hand to tighten his grip.
Coutts said: "I asked her if she wanted to try something different."
He took a pair of tights from the floor and explained some "ground rules": If she felt uncomfortable or if the ligature was too tight or hurting her she was to tell him and he would stop.
He told the court: "She replied in the affirmative."
Coutts demonstrated to the jury what happened next.
He tied a blue ribbon round a washing-up liquid bottle, making a half knot in front.
He said he had held the two ends of the tights behind Miss Longhurst's neck.
Coutts wiped his eyes as he told how Miss Longhurst suddenly collapsed dead.
He said his next recollection was being in the lounge: "It is difficult to explain this next part.
"It is almost like a picture, a photograph, like someone standing outside the lounge had taken a picture of me in silhouette. I'm sitting on the sofa."
Coutts tried telephoning his partner Lisa Stephens, pregnant at the time with twins. He was frightened she might return and see what had happened.
Jeremy Gold QC, defending, asked where the body was at this point.
Coutts replied: "I have this image of a box with a body inside in a foetal position."
Minutes later, Coutts was on the phone again, this time to a colleague with Kleeneze, the cleaning goods firm he worked for.
When Coutts was asked why, he said: "I don't know. I would catch myself saying 'this isn't happening', I went into auto-pilot . . . to do the normal things I would have been doing."
He bought tarpaulin at Wickes Building Supplies in Davigdor Road and wrapped it round the box containing the body. He put the box in the car boot.
Coutts said he had a "picture, a sort of third-person thing, seeing myself with a tarpaulin object which is heavy, struggling out of the door."
Mr Gold asked: "I don't doubt everyone in court will be asking this, so I will ask you.
"Bearing in mind this terrible tragedy had happened, Jane had died in your flat, why did you not do something decent and responsible about making this known?"
Coutts replied: "My worry was that Lisa would come walking through the door.
"Lisa had an eight-week scan two days before and if she had walked through the door and seen Jane there was a high risk she would have lost the babies with shock."
Coutts said he drove around the rest of the day and contemplated going to Beachy Head to throw himself over the cliffs.
He drove past Brighton police station and thought of going in and telling them.
What stopped him, he said, was the thought of Lisa.
He said she had undergone fertility treatment and he was worried she would miscarry.
He drove home and sat with his partner watching Comic Relief on TV.
Coutts said he could not remember details but he must have gathered up Miss Longhurst's clothes and belongings before Miss Stephens returned home.
The next day he intended leaving the body in the countryside but it did not seem right.
Miss Longhurst's partner Malcolm Sentance telephoned in the morning asking if he had seen her.
Mr Sentance was desperate with worry but Coutts said he told him nothing.
That night he hid the body in a brick shed in a yard at the rear of his flat.
He visited the body twice.
Mr Gold said: "It may be suggested you kept Jane's body as some sort of trophy or part of a bizarre and macabre sex fantasy."
Coutts said: "No."
Mr Gold: "Did you gain any satisfaction from seeing the dead body of Jane Longhurst? Coutts: "No."
Miss Longhurst's body was discovered on fire in woodland near Pulborough 35 days after she died.
Mr Gold asked: "Did you ever look at her body again before the day of the fire?"
Coutts said: "No."
Earlier, Coutts was asked if he was turned on by the thought of sex with dead bodies. Again, he said no.
Eleven days after Miss Longhurst's death Coutts transferred the body to the Big Yellow self-storage warehouse in Brighton.
He told the court: "I did not know what else to do with the body. I could not put it in the car boot or the shed or leave it somewhere else."
Asked why, Coutts replied: "She was alive a few days before and she was my friend.
"I found myself in the situation which was pretty horrific for me. To leave the body in the countryside . . . I could not bring myself to do that.
"It just did not seem right."
The trial continues on Monday.
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