A teenager has been jailed for at least 16 years after being found guilty of murdering a high-ranking civil servant at his country cottage after they met via the gay dating app Grindr.

A judge said Ben Bamford, then 17, caused "merciless carnage" by using at least three knives to inflict more than 40 stab wounds on senior HM Revenue and Customs official Paul Jefferies, 52, including slashing his throat.

Mr Jefferies, who reportedly advised ex-chancellor George Osborne's Treasury team, was found naked with a tea towel over his head on his blood-covered kitchen floor in Coggins Mill Lane, Mayfield.

Bamford had set out to get money from openly gay Mr Jefferies on February 23 after being pressurised to pay drugs debts of about £400 within days, a two-week trial at Lewes Crown Court heard.

Bamford, now 18, denied murder, claiming he was protecting himself from Mr Jefferies who had "come on to him" but jurors convicted him on Tuesday after three hours of deliberation.

After leaving Mr Jefferies for dead at his Grade II listed cottage, Bamford locked up the house and stole his Audi TT car and picked up a friend en route to Eastbourne District General Hospital.

Blood-spattered Bamford then posed for an obscene selfie picture less than three hours later while flicking his middle finger on his hospital bed after telling staff he had self-harmed so the police would not be called.

Sentencing Bamford, of South Street, Crowborough, Mr Justice Spencer said he murdered him in a drug-fuelled "outburst of extreme violence" possibly over money or sex.

Mr Justice Spencer told Bamford: "In total you inflicted in excess of 40 knife wounds to the head and body of Paul Jefferies with at least three knives.

"They included stab wounds to his face, close to the right eye and to his forehead where the knife scored the skull."

He added: "The overall attack must have lasted several minutes, during which time he was conscious and mobile.

"You must have realised by the end that he was fatally injured. You placed a tea towel over his head and shoulder as he lay dying on the floor, probably because you could not bear to look at what you had done."

The judge said Bamford's account of what happened only revealed "a fraction of the truth".

He went on: "The reality is that you must have stabbed him many times in the bedroom, in an outburst of extreme violence, as the photographs clearly demonstrate.

"Precisely what triggered that outburst we shall never know unless and until you choose to disclose it. It may have been to do with sex. It may have been to do with money."

Mr Justice Spencer said it was in the kitchen where "the final merciless carnage took place", adding that Mr Jefferies said and did nothing to "excuse or explain" the killing.

The judge said Bamford failed to summon help after the stabbing but added that he accepted the teenager had not attempted to rob Mr Jefferies.

"You undoubtedly went to the house only in order to persuade him to give you money," Mr Justice Spencer went on. "It was not because you wanted to have sex with him, although you knew that was bound to happen."

Mr Jefferies, described by colleagues as "diligent, personable but very private", moved to Sussex from London about five years before his death following the breakdown of a relationship.

Prosecutor Jeremy Carter-Manning QC said that as a young man, Mr Jefferies abandoned a plan to pursue a career in medicine and joined HMRC in a "pretty basic" role.

He added that Mr Jefferies' abilities were recognised and he worked his way up to enjoy an "impressive" career as a civil servant.

No victim impact statement was prepared for the sentencing hearing as, since his early 20s, the "shy and private" Mr Jefferies had been estranged from his family who refused to accept his homosexuality, a rift which had a "profound" impact on him, the court heard.

Bamford's defence counsel Alan Kent QC said that on the night of the murder, "something must have happened to cause this eruption of violence".

In mitigation, Mr Kent said: "This is not an evil young man in any way. This was unplanned and spontaneous.

"No weapon was taken by him to the cottage that night. This demonstrates that this was not a planned killing."

Bamford, the middle of three brothers, came from a "loving and stable family", Mr Kent went on.

In front of Bamford's parents, Richard and Annmarie, who sat side-by-side in the public gallery, Mr Kent added: "It's a tragedy for them that he has been convicted of murder."

Bamford met Mr Jefferies through Grindr two years before the killing, when he was 15, and resumed contact in December 2015 following a break.

Unknown to Mr Jefferies, by the time they met again, Bamford was desperate for money to settle drug debts and was being pressured by a dealer called Glen.

Text exchanges between Bamford and Glen were read during the trial. One, sent on the day of the killing, read: "I'm not happy. On my boy's life, I will see you today."

In another exchange, Glen accused Bamford of "treating me like a mug". Bamford replied: "I will get it to you. Don't worry."

During his defence, Bamford told the court he had met Mr Jefferies in the hope that he would give him money, as he had done in the past.

Bamford claimed he stabbed him to protect himself after Mr Jefferies "got on top of me" and carried on having sex with him after Bamford told him to stop. Bamford said Mr Jefferies only stopped when he told him he needed the toilet.

Bamford said he then went downstairs in his boxer shorts as he "wanted to get away" from Mr Jefferies, but found the door locked.

He told the court: "I knew that all my stuff was upstairs, like my phone, so I knew I had to go upstairs at some point. I ended up taking a knife. It was on the kitchen side."

Nurse Mrs Bamford told the trial she was "dumbfounded" after her son told her he had killed someone as he recuperated at home following an operation for his injuries.

She told jurors: "I kept saying that I need to know what's happening. And then he shouted, 'I think I've killed somebody'.

"I had to ask him again because he was being very tearful and angry. I asked him again in disbelief - 'What?'.

"And he said again, 'I think I've killed somebody'. He then went on to his bed and laid there face down, very upset and very tearful."

Mrs Bamford went online to find anything to support what he was saying, and found a report of a suspicious death in Mayfield.

"I said to Ben, 'We need to go to the police', and he said, 'Yes, I know'," said Mrs Bamford.