A MUM accused of murdering her three-year-old daughter said she drowned the little girl in the bath to "save her" after separating from her executive husband who she feared was having an affair, a court has heard.

Claire Colebourn is accused of drowning Bethan at their home in Fordingbridge after the 36-year-old split with husband, Michael, the CEO of marine interior company Trimline.

Kerry Maylin, prosecuting, told Winchester Crown Court today that Bethan was found by her grandmother, Janet Fildew, when she arrived for a visit to the family home in Whitsbury Road on October 19 2017.

Ms Maylin said: "Bethan was three.

"She was a much loved daughter of Claire and Michael Colebourn, but she was found dead at her home.

"Claire Colebourn, when Bethan was found, was also in the house and she was at the time suffering a diabetic episode.

"Bethan died because she had been put in the bath at home and held under the water. The act was completed by her mother."

Ms Maylin said that in a nine-and-a-half-hour period that day, Colebourn had administered a dosage of insulin 10 times that she would normally use in a whole day.

The prosecutor said that just over a month before Bethan's death, Colebourn and her husband, who had been together for 16 years and married for six years, separated and Mr Colebourn had moved out.

It was alleged that the couple's relationship had been difficult. The defendant went on to make "unfounded accusations" on Facebook and in an email sent to his work that her husband was having an affair with the company's finance director Kelly Futcher, it was claimed.

In the email to Trimline, Colebourn allegedly wrote: "He has been having an affair with his finance director at work, everything has been pre-planned, of course the finances.

"They are aiming to take over the business and set up a new life together."

Colebourn also told friends she had visited Ms Futcher's home looking for her husband's car.

Ms Maylin alleged Colebourn also became worried, without foundation, that Mr Colebourn was monitoring her computer and arranged for an IT firm to supply her with a new laptop and wifi at her home.

Within minutes of receiving the new computer in October, the defendant began searches for suicide-related websites and another website called How To Kill By Drowning, as well as watching a YouTube video titled Someone Drowns In A Tub Nearly Every Day, the court heard.

It was claimed that on the day before Bethan's death, Colebourn also wrote a letter to her mother saying: "I love you, Bethan loves you, thanks for everything. Please make sure Walter (horse) and Charlie (dog) are looked after. Love always, Claire."

She added: "Please make sure I am buried with Bethan in Fordingbridge," it is alleged.

Ms Maylin said a doctor described how Colebourn was "only emotional when discussing the fact Michael Colebourn had left her and her daughter and her father had done the same to her mother".

The defendant allegedly later told police: "I am responsible for Bethan's death because she drowned and I am responsible for it.

"Bethan drowned because I was there, I held her under the water."

She also made accusations that her husband had been "controlling and a bully".

It was claimed that the defendant told police: "I ran a bath, she went into the bath, and I held her under the water surface."

Ms Maylin said: "[Colebourn] said she held her hand to hold her under the water.

"She said she did it because 'I didn't want her to go anywhere near her father'.

"She confirmed when Bethan came out of the water she was already dead. She said she took her to the downstairs bedroom, wrapped her under her arm and then injected herself with insulin."

olebourn said "her only aim was to keep Bethan safe", it was said.

Describing the incident, Colebourn allegedly said: "She put her hand on my cheeks, told me she loved me and said, 'I do not want a bath, I do not want a bath'.

"I waited for the bath to fill, I have never been so stressed in my life. I drowned my own daughter, I drowned my own daughter."

Ms Maylin added that Colebourn said her daughter did not struggle and she added: "She didn't fight against my hand. I think, very sadly, she had complete trust in me."

The last time Mr Colebourn saw his daughter alive was when he took her to a soft play centre.

He told jurors: "Claire wasn't very happy I was seeing Bethan but eventually allowed me to have the afternoon, but it wasn't a very nice experience.

"Claire wasn't very keen to give Bethan to me and started to say, 'Why are you doing this?', and tried to prevent me from taking Bethan, which upset Bethan."

Colebourn denies murder and the trial continues.