The father of a five-year-old boy murdered by his mother, stepfather and a 14-year-old boy has asked why his son had to die in such horrific circumstances.

In April, Angharad Williamson, 31, John Cole, 40, and the youth were convicted after a 10-week trial at Cardiff Crown Court of murdering Logan Mwangi.

They will be sentenced on Thursday.

The boy’s body was found in the River Ogmore in Pandy Park, Bridgend, South Wales, on the morning of July 31 2021.

He had more than 50 external wounds, as well as multiple internal injuries akin to those found in victims of a fall from height or high-speed car crash.

Logan’s father, Ben Mwangi, had been denied contact with his son since April 2019 – around the time Williamson began her relationship with Cole.

Speaking to ITV, Mr Mwangi said: “What child has to go through that sort of torture for such a long period of the time? No, it really doesn’t seem real.

“One of the biggest questions in my whole entire life I’ll always be asking myself is, ‘Why? Why did this happen? Why did Logan have to die?’”

Cole was obsessed with the idea Williamson had cheated on him with Mr Mwangi, witnesses said.

The defendant reportedly used a racial slur to describe his step-son, and had links to the National Front.

Mr Mwangi said Williamson stopped him seeing Logan.

“She blocked my number. For the past five years, I’ve been struggling and trying to fight just to see Logan. She made my life an absolute misery. All I’ve wanted to do was just be a dad,” he said.

Just a month before Logan was killed last July, social workers in Bridgend removed him and a younger sibling from the child protection register – meaning they were no longer believed to be at risk of serious harm.

But Logan had suffered “catastrophic” internal injuries consistent with a “brutal and sustained assault”.

The day before police found his body, a social worker spent 20 minutes outside Logan’s home speaking to the three defendants, but did not see or hear him.

Mr Mwangi was not told his son was on the child protection register and wants the law changed so social services have a duty to inform estranged parents.

He said: “I probably would have tried to take him away. Why didn’t they do anything to make it a safe environment for him when it clearly wasn’t?

“If I can stop this from happening to anybody else, then that will be the biggest, positive, most positive thing. My lasting memory of him was just a happy little boy that called me ‘Daddy’.

“The wonderful memories I have with my son will never be tarnished. They will forever be in my heart and soul.

“I loved him so much and somehow I have to live my life knowing that I will never get to see him grow up to be the wonderful man I know that he could be.”

A child practice review has been launched into Logan’s death and will be led by the Cwm Taf Morgannwg Safeguarding Board, which includes local councils and the police, probation service and NHS.

An ITV documentary, The Murder Of Logan Mwangi, was produced in conjunction with South Wales Police.

It starts at 9pm on Thursday.