Julie Dixon, 43, to serve a minimum of 23 years for killing David Twigg, 46, by locking him in business premises she set fire to

A woman has been jailed for a minimum of 23 years after she murdered her fiance by locking him in a storeroom at his workplace and setting fire to the building.

Julie Dixon, 43, was handed a life sentence after she originally denied the murder of joiner David Twigg and claimed they were both attacked by two masked intruders who were responsible for his killing on the night of 13 Marchlast year.

On the second day of her trial at Lincoln crown court last month, Dixon changed her plea to guilty and admitted killing 46-year-old Twigg ? first saying his death was the result of a failed joint suicide pact, only to later change that story to claim Twigg had wanted to die and she had assisted his suicide.

Twigg was found dead in a locked storeroom cupboard at his business premises in Burgh le Marsh, near Skegness, Lincolnshire. He died as a result of smoke inhalation and the products of combustion.

A Newton hearing was held by Judge Michael Heath following Dixon's change of plea to establish the facts and motive in the case.

Giving his ruling on Tuesday after the hearing concluded on 23 December, the judge told Dixon he rejected her story that Twigg had wanted to die and branded it a "pack of lies".

He said: "Her performance in the 999 call and to the emergency crews at the scene, including to the firefighters and at the hospital would have been worthy of the highest praise had she been an actress in some fictional drama and would have warranted an Oscar nomination."

He added: "I am sure that this was not an assisted suicide. I am sure it was a premeditated killing.

"David Twigg did not want to die."

Heath called Dixon an "unreliable and incredible witness" and said he was sure from evidence that she bought the petrol that was used to set fire to the premises, that she struck the match that started the blaze and left Twigg to die, and that she planted keys on a neighbour's land and mentioned to others a dispute with them in order to try to place suspicion elsewhere.

The court heard that Dixon and Twigg, who had been in a relationship since 1996, ran the bespoke joinery business together. Twigg handled the practical side of it while Dixon was responsible for all administration and financial duties.

Using funds from her divorce settlement and family input, Dixon purchased the land in Burgh le Marsh in 1997 but the business struggled and Twigg was eventually declared bankrupt in October 2010.

The court heard that he owed Her Majesty's Revenue and Customs ?37,500.

Dixon did her utmost to conceal from Twigg the debts that were being amassed and went so far as to tell officials who wanted to talk to him about his financial situation that he was ill or working abroad.

Heath said: "She was resourceful and imaginative in her dealings with the insolvency service."

The court heard evidence that Dixon had mentioned to friends that she was unhappy in her relationship with Twigg.

There were also internet searches on the couple's computer carried out in December 2010 under the username "Julie" looking for: "The thing that kills you and does not show on a postmortem" and: "How can I disguise tablets in food?"

Another one searched for an answer to the query: "I've tried to disguise tablets in chocolate syrup but it still does not work."

The court heard that chocolate syrup was ordered online and signed for by Dixon upon its delivery.