'Ruthless' Surrey killer Paul Cryne was caught by DNA

Mrs Birchwood was last seen alive, walking with the aid of a stick, at Guildford library

Sharon Birchwood was described in court as a quiet woman who lived an ordinary life, beset by ill-health.

So detectives were baffled when the frail 52-year-old was the victim of what appeared to be a professional hit at her home in a quiet part of Surrey.

Her ex-husband, Graham Birchwood, who stood to gain £475,000 on her death, was jailed for murder last June.

The last piece in the jigsaw was put into place on Tuesday when Paul Cryne was found guilty of carrying out the killing.

Months of painstaking detective work and a crucial DNA breakthrough helped bring Cryne to justice.

The lengthy investigation began when Mrs Birchwood's body, "cruelly trussed up", was found at her bungalow in Harriott's Lane, Ashtead, on 4 December 2007.

Detectives were initially suspicious of her former husband who had debts of more than £150,000, but Birchwood had an alibi.

Ruthless efficiency

On the day of the killing, he was pictured on CCTV in the Ashley Shopping Centre in Epsom.

Police needed to know more about Mrs Birchwood's life and distributed 6,000 leaflets to residents and businesses.

The many people who came forward with information painted a picture of a quiet woman with no apparent enemies.

Graham Birchwood was known by his middle name of George

She had no children, a limited social life and was so devoted to her former husband she continued to sign his name in Christmas cards.

Some of her friends thought the couple were still married though they had divorced in 1989.

There were no signs that she was killed during a struggle or in a robbery nor was there any sign of a sexual motive.

Police released a CCTV image of the last time Mrs Birchwood was seen alive in the hope of jogging people's memories.

The grainy pictures show her with walking stick and trolley, visiting Guildford library and later the town's railway station.

'Cold-blooded execution'

It was Birchwood's friendship with Paul Cryne, a former business associate living in Thailand, that began to raise suspicions.

Cryne, 62, had flown to Heathrow from Thailand on 26 November and stayed with Birchwood's mother in Banstead.

The pair, who were in mobile phone contact throughout his stay, were said to have hatched a plan to secure Mrs Birchwood's "pot of gold".

Prosecutors said Cryne's final call, on the evening of 4 December, was made to inform Birchwood "the fatal deed had been done."

Sharon Birchwood was registered disabled and walked with a stick

Within hours of the murder, Cryne was back at Heathrow, awaiting a flight to Thailand the next morning.

The court heard he carried out the killing with "ruthless efficiency", leaving no fingerprints or obvious clues.

But prosecutor Mark Dennis QC said Cryne left behind one crucial piece of evidence.

"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 (Cryne)," he said.

Birchwood was jailed for a minimum 32 years after being found guilty of ordering the "cold-blooded execution" last June.

Cryne was extradited from Thailand to face trial at the Old Bailey.

After the first trial, Mrs Birchwood's relatives spoke of their "nightmare" at discovering the facts of the chilling plot.

Now the killer is also behind bars, police hope the family can begin to rebuild their lives.