A British expatriate flew home from Thailand to strangle a devoted housewife so her ex-husband could inherit a "pot of gold" of nearly £500,000, a court heard today.

Sharon Birchwood, 52, was left "cruelly trussed up" with parcel tape and electrical cord on her bed by Paul Cryne, a jury was told.

Cryne is alleged to have carried out the murder in Ashtead, Surrey, on behalf of Graham Birchwood, who had gone shopping in Epsom at the time.

He carried out his work with "ruthless efficiency", leaving no fingerprints or any other "obvious clues" and was only caught after a "painstaking" forensic investigation, the Old Bailey heard.

Birchwood, 54, had found himself heavily in debt and facing bankruptcy after a string of business failures in Thailand, the court was told.

Mark Dennis QC, prosecuting, said: "His only hope was if he found a pot of gold, enough money to clear his debts and start over again."

Jurors were told that he has since been found guilty of the murder. Cryne, 62, who was later extradited from Thailand and is now on trial, denies the charge.

Mr Dennis said Birchwood was the sole beneficiary of his ex-wife's will, leaving him her £400,000 bungalow and £75,000 in life insurance.

This would leave "more than enough" to pay off the mortgage and he would be free to return to Thailand, jurors were told.

But he realised he would fall under suspicion if she were to be killed and needed someone "prepared to do such a deed without being noticed, who could disappear without ever attracting the attention of the police", Mr Dennis said.

All he had to do was "keep a cool head" and appear to assist the investigation, the court heard.

"Had it not been for some painstaking forensic work, Birchwood would have got away with this," said Mr Dennis.

"However careful the killer had tried to be, as it turned out, there was a clue left behind.

"DNA traces from the right hand of the deceased and the roll of tape used to bind her were recovered and found to match the DNA of this man, the defendant."

The court heard that Cryne was "a man who for many years had been living in Thailand, part of Birchwood's expat business circle, a man who was also short of money and who was prepared to do such a deed".

Cryne flew in from Thailand at the end of October 2007 before going to stay with Birchwood at Birchwood's mother's house in Banstead, Mr Dennis said.

Two days before the killing in December, he left, giving the impression he was going to stay with friends in the West Country but in fact he did not go far and was a short distance from Ashtead, jurors heard.

Mrs Birchwood was said to have been murdered after returning home from Guildford, and within three hours, Cryne was at Heathrow awaiting a flight back to Thailand the next day, the court was told.

The victim's ex-husband "tried to cover his tracks" by sending text messages to her on the following two days, before a 999 call the day after that.

An ambulance crew found Birchwood standing outside the bungalow holding a cup of coffee, before going inside.

"Fifty-two-year-old Sharon Birchwood was found lying fully clothed on her bed, cruelly trussed up," said Mr Dennis.

"She had been bound and gagged using a combination of parcel tape and electrical cord. Her ankles had been tightly bound together by tape as had her wrists."

Mrs Birchwood's wrists had been pulled up to her face and she had been gagged.

"Electrical cord had been repeatedly wrapped around her head and a small metal handle had been used to tighten those bindings acting in effect as a tourniquet."

There were no signs that she was killed during a struggle or in a robbery or that there was any sexual motive, the court heard.

"The victim had been taken completely by surprise in her own home and had been incapacitated almost immediately," said Mr Dennis.

He said the actions of the killer were those of someone intending to kill Sharon Birchwood, "something which was achieved with ruthless efficiency".

The court heard that Mrs Birchwood was a "harmless, ordinary person" who had not moved on after divorcing her husband in 1989 and remained "devoted" to him - despite the fact he went on to marry and have two children with his secretary.

"He, on the other hand, was not so devoted, and he on occasions used her to his own advantage," said Mr Dennis.