Robert McWhir jailed for minimum of 18 years after being found guilty of murdering mother-of-two Marissa Aldrich

Marissa Aldrich, from St Neots was pronounced dead on December 22. (Image: Archant)

St Neots man Robert McWhir has been found guilty of murdering 29-year-old Marissa Aldrich following a trial at Cambridge Crown Court.

McWhir, 26, from Potton Road, St Neots, drowned Ms Aldirch after holding her head in a pond containing just 10cam of water at Love's Farm in the early hours of December 22 last year.

There were emotional scenes from Ma Aldrich's family as the jury foreman announced the guilty verdict, but McWhir just starred straight ahead and shook his head. The jurors took 10 hours to reached their verdict and the judge accepted a majority of 11-1.

Judge David Farrell announced he would be passing sentence immediately and told McWhir: "You have been convicted by the jury of the offence of murder. The victim was only 29, a young woman, a mother who you had an on-off relationship with. This was a murder committed by you out of jealousy and possessiveness because you believed Marissa was still seeing her former boyfriend.

"Both of you took the route that was well known to you that night. On that route as you approached the bridge, you and her undoubtedly began arguing, you took her phone, grabbed her and ended up in the drainage ditch with the relatively shallow water and deliberately drown her. Intending to kill her and kill her you did. I am satisfied that you intended to kill her."

McWhir also received three years for conspiring to pervert the course of justice after he attempted to blame the murder on someone else. He made a telephone call from prison, which had been recorded. Judge Farrell said this sentence would run concurrently with the murder sentence.

Judge Farrell also commended the actions of Ben Cornwell, the passing motorist who was flagged down at the scene and helped Tracey Underwood pull Ms Aldrich from the pond. He attempted to give Ms Aldrich CPR at the scene. Judge Farrell described Mr Cornwell as a "good samaritan" and said he was recommending he received £750 from the High Sheriff of Cambridgeshire in recognition of his bravery.

During the trial the jury heard McWhir was "jealous and controlling" and told Ms Aldrich he wasn't going to be "anyone's second best" after he found out she had been seeing another man. Ms Aldrich was found face-up in the drainage pond and by the time she was discovered she was in cardiac arrest and had stopped breathing. Attempts were made to revive her at the scene and she was taken to Hinchingbrooke Hospital where she was pronounced dead at 3.54am.

In the hours before the murder, McWhir and Ms Aldrich had been having -pre-Christmas drinks at friend's flat on Cambridge Road.

McWhir was said to be "angry and agitated" throughout the evening.

The pair left the party at around 2am and were arguing. The argument turned physical and Ms Aldrich ended up in the balancing pond in Loves Way. McWhir then pressed Ms Aldrich's face down in 10cm water,

As he continued to hold her under the water he received a telephone call from a friend and told him "I'm killing her, I'm killing her" and "she's talking to other blokes behind my back".

Once the friend, Luke Holder, got to the scene he saw McWhir "kneeling on her back and pushing her head in the water".

He then wrestled with McWhir to get him off Ms Aldrich, but she was already dead.

McWhir then fled the scene, and was arrested by police at Dramsell Rise in Loves Farm at around 4:45am.