Ross McCullam, 30, and Megan Newborough, 23, had been seeing each other for about a month when he killed her last year.

He throttled her then cut her throat with a carving knife, later telling police he did so "to make sure Megan was dead".

McCullam then dumped Ms Newborough's body close to a country lane in Leicestershire before trying to cover his tracks by leaving a voicemail on her phone telling her that he loved her.

He was found guilty of her murder at Leicester Crown Court on Monday after a six-week trial.

Ms Newborough's family said their lives have "well and truly been ripped apart" after the verdict.

During the trial, John Cammegh KC, for the prosecution, branded McCullam a "sadistic killer" who had acted with "ruthless" intent.

After his conviction, police described McCullam as a "wolf in sheep's clothing" and believed he would have "gone on to kill again".

McCullam met Ms Newborough while working for a brick-making firm.

On the evening of 6 August last year, Ms Newborough left her home in Nuneaton, telling her family she was meeting McCullam for a walk.

She drove to the home he shared with his parents in Coalville. Both his parents were out.

Within 40 minutes of her arrival, he had murdered her.

McCullam then undertook a "series of deliberate actions carefully calculated and executed to cover up Megan's murder", the trial heard.

That included sending text messages to her phone, including one telling her she was amazing.

It was sent at the same time as he was bundling her body into the passenger seat of her own car.

Having driven away, he disposed of her phone in undergrowth before dumping her body over a stone wall near the village of Woodhouse Eaves.

McCullam then drove to Loughborough, where he was caught on CCTV changing his clothes.

He took a taxi home and arrived back soon before his parents returned.

He searched the internet for pornography and looked up details of serial killers in the hours after he disposed Ms Newborough's body.

Police found he conducted online searches linked to serial killer Levi Bellfield, Soham killer Ian Huntley and Yorkshire Ripper Peter Sutcliffe.

At around 11.30pm he called Ms Newborough's phone and left a voice message telling her he loved her and, knowing she was dead, said: "I had a fun time earlier."

McCullam had previously admitted manslaughter but denied murder, claiming he acted out of "blind rage" after remembering sexual abuse from his childhood, which triggered a moment of post-traumatic stress disorder.

But the prosecution dismissed his claims as a "pack of lies" and said McCullam murdered Ms Newborough because of his anger at being sexually impotent immediately prior to the attack.

Prosecutors pointed to his having ordered tadalafil pills off the internet, used to treat erectile dysfunction.

On remand, McCullam had also bragged to a cellmate about using the knife, and suggested he would use his mental health as a "tool" at trial.

In another incident, he was overheard on a prison landing by a guard laughing as he told other inmates "If you carry on like this, you'll end up like Megan".

Another prison warder also heard him joking openly with other inmates about the killing, telling them "if I had gone a bit further I'd have taken her head off".