A devious paedophile who murdered a 15-year-old girl to stop her reporting their sexual contact has been jailed for a minimum of 33 years.

Robert Ewing exploited vulnerable Blackpool teenager Paige Chivers for his sexual gratification and then decided to silence her when she threatened to go to the authorities.

A jury at Preston Crown Court convicted the 60-year-old of her murder earlier this month but was not told that Ewing had previous convictions for child sex offences.

Ewing served a 12-month jail sentence in 1995 for gross indecency with a 13-year-old girl, whom he also indecently assaulted.

Sentencing him to life, Mr Justice Jeremy Baker told Ewing he had carried out a "carefully planned and executed murder" to avoid the prospect of returning to jail.

Ewing, who smiled for his police mugshot photograph, sat with his arms folded for most of the hearing and calmly walked from the dock after sentencing.

The body of the teenager has still not been found nearly eight years after she went missing.

Mr Justice Baker said Paige's life was "in turmoil" in the summer of 2007 after her mother had died in February that year and her late father's addiction to alcohol worsened to the extent that he largely abandoned her.

He said she was "sexually promiscuous" and an "easy target", which was recognised by Ewing, whose flat near her home in Bispham became "something of a magnet" for young girls as he allowed them to smoke, drink alcohol and take drugs.

The judge said: "There came a point when Paige Chivers realised that she could manipulate the situation to her advantage and threatened to report you to the authorities ... the last thing you wanted to occur was for the public authorities to be acquainted with what you had been doing."

Less than a fortnight before Paige went missing, Ewing contacted police to tell them that a "problem child'' had turned up on his doorstep, having been thrown out by her father.

Prosecutors said he was effectively "testing the water" and there had been "very little reaction" by officials.

The judge, who labelled the defendant "intelligent and devious", also wanted to create an "innocent cover story".

He told the court that the precise circumstances of Paige's death may never be known in the absence of any explanation from Ewing.

But the judge noted that Ewing had been heard in a covert police recording saying: "You don't mess with me. Quick hammer over the f****** head, then they will be sorry."

Only three tiny spots of blood belonging to Paige were found by police in inner hallway of his flat in All Hallows Road, after a meticulous clean-up by the defendant.

On August 23 2007, Paige left home with clothes a row with her father over missing money. She was seen at a bus stop by Paige.

Ewing persuaded his friend, Gareth Dewhurst, 46, to use his car to dispose of the body.

Dewhurst was jailed for seven years for assisting an offender and an additional year for intending to pervert the course of justice