A man killed his girlfriend during an outdoor sex session after drinking 45 pints of beer in 36 hours.

Lee Portwine, of Pound Hill Parade, Crawley, admitted murdering Una Whitney by stuffing mud in her mouth and headbutting her after they went to have sex in woods.

The couple, both 38, had consumed large amounts of alcohol and drugs when they left a friend's wedding reception on July 26 last year.

They walked into woods near the Gatwick Worth Hotel, near Crawley, but a fierce argument broke out.

Portwine, who lived with Whitney in Crawley, pleaded guilty to murder during a hearing at Lewes Crown Court yesterday.

Paul Lewis, QC, prosecuting, said Portwine had pushed earth into the care assistant's mouth and then headbutted her because he was embarrassed someone might hear them arguing.

They argued when Ms Whitney began shouting that he was hurting her during sex.

Mr Lewis said Portwine later told police: "We were into the asphyxiation thing where you get a buzz when you can't breathe."

Portwine told police he and Ms Whitney had taken Ecstasy during the evening. Tests showed Ms Whitney had enough alcohol in her blood to make her three times over the drink-driving limit.

They also showed a single headbutt would only account for some of the injuries and that Ms Whitney had been hit more than once.

The tests showed she had probably choked to death on the mud while unconscious, Mr Lewis said.

A bite mark was also discovered on Ms Whitney's left cheek.

Mr Lewis said the couple had a stormy relationship. He said: "The relationship appears to have been violent.

"The deceased was frequently seen with black eyes which she told friends he had caused.

"It appears the defendant was a possessive man and did not want the deceased to have close friends.

"Sometimes he would lock her in the house."

After the attack Mr Lewis headed back into the hotel.

He told the bride, who was still drinking in the bar: "I headbutted her and I split her head open. I can't wake her up."

Portwine handed himself into police the following morning.

Sentencing Portwine to life in prison, Mrs Justice Rafferty said: "It is clear that in late July 2003 drugs and alcohol raised their ugly head in miserable circumstances leading to the death of Ms Whitney.

"The relationship had turbulent aspects. If only that was all her loved ones had to bear."

The judge said the minimum sentence tariff would be decided after probation service reports.