A mother accused of murder sobbed as she described the moment her boyfriend punched her five-year-old son in the stomach and told her he would “kill him” if she ended the relationship.

Logan Mwangi, also known as Logan Williamson, was discovered in the River Ogmore in Pandy Park, Bridgend, on the morning of July 31, 2021, just two days after the alleged assault took place.

Angharad Williamson, 31, claims Logan, her child from a previous relationship, was attacked by her partner John “Jay” Cole, 40, and a 14-year-old youth, who cannot be named because of his age, on the Thursday before he was found dead.

She told Cardiff Crown Court that the incident happened after an argument between herself and Cole over someone spilling a drink on her stereo.

Giving evidence, Williamson said: “It escalated quite quickly. I showed him my stereo and he said straight away it could have been Logan and I said ‘why do you pick on Logan?’. I started shouting.

“Jay said Logan had smirked at him and turned around and said, ‘You love it when me and your mum argue. You think it’s funny’. He called Logan out of his bedroom and into the hallway.

“He tried to talk to him and Logan stuttered and he wouldn’t talk to Jay.

“He stuttered again and Jay punched him twice in the stomach, he fell on his bum and hit his elbows on the floor. I went forward and he was blocking the doorway to the kitchen.

“I said, Jay leave him alone. He asked for [the youth] to come from the living room into the hallway and said ‘If he flinches again or stutters, sweep him’. He did and he pushed his head to the ground.”

Williamson said she ran into the living room to get her phone but could not find it so ran from the house to call for help.

She said: “I told Logan to get in his bedroom and stay there. I wanted to call my mum or (friend) Rhiannon to get help for Logan.”

In a video played to the jury, Williamson is seen running out of the flat where the family lived in Lower Llansantffraid, Sarn, just before 3pm and being chased by the youth defendant. After a few moments she can be seen to go back inside.

Williamson said Jay managed to calm her down but that it was her intention to leave for good.

“I’d had enough. He’s crossed a line hurting Logan,” she told the court.

Asked if she had told Cole she wanted to leave him, she added: “I told him that a bit later.

“He said ‘If we break up because of Logan I’m going to kill him’.”

Throughout the course of the next day Williamson said Logan did not seem in pain or discomfort, although he had refused to eat his favourite meal of pizza and chips on the Friday evening.

She said after putting him to bed she took her medication and went to sleep at around 10pm, while Cole and the youth played an Xbox in the living room.

When she woke around 5.30am, Logan was not in his room and she began looking around the flat and outside for him, eventually calling the police.

Peter Rouch QC, defending Williamson, said: “The prosecution suggest what happened then was a sham by you and make believe. Is that true?”

Williamson said: “You can’t fake feelings like that.

“I was so scared. My worst nightmare had come true. He was gone, I didn’t know where he’d gone. I didn’t know if he was safe. He was my little boy and he was out there on his own.”

Mr Rouch said: “When you got up in the morning did you know what had happened that night? John Cole taking Logan’s dead body to the river?”

Williamson said: “No, I didn’t.”

When interviewed by detectives in Bridgend Police Station, Williamson said she did not tell them at first about the assault on the Thursday because she was scared of Cole, who she claims told her he was in the SAS and had been in prison.

Under cross-examination by Cole’s defence counsel David Alias QC, she said: “I didn’t want to believe the man I loved so much could do this to my son.

“I do now due to the autopsies.”

Mr Alias said: “Mr Cole was a phenomenal dad.”

Williamson replied: “At the beginning. That changed when he started getting stricter with Logan. When he was good he was good, but when he lost his temper he was bad. It was when he got more comfortable in our relationship and in the family home, he got stricter and angrier.”

After being charged with perverting the course of justice, then murder, Williamson was taken to Eastwood Park, a female prison in south Gloucestershire. There, she said she experienced being called a “child murderer” and threatened by the other inmates and had to be segregated from the general prison area for her own protection.

Cole has admitting perverting the course of justice for dumping the boy’s body, but denies murder.

He is on trial alongside Williamson and the 14-year-old, who deny all charges against them.

The trial continues.