A self-styled ‘evil black witch’ from Wellington has been jailed for life for a sadistic sex attack which left an elderly shopkeeper in excruciating pain.

Former Cambridge University researcher David Lake wore a bizarre carnival-style mask during the attack in which he kicked his victim unconscious before inserting an object into his body.

He was ruled to be a danger to the public because he carried out a previous cannibalistic attack in which he chewed flesh off a woman’s arm and ate it.

He posed as a customer at the shop in Exeter in October 2018 before returning with alcohol and offering it to his victim, who is in his 70s.

He plied the shopkeeper with vodka and champagne before putting on the gold mask and suddenly turning violent.

He said: “I am a black witch. I am not a nice person. I’m a black sorcerer and I am f***ing evil.”

He battered the victim to the ground and kicked him in the back until he passed out from the pain caused by a fractured coccyx. He sexually assaulted him with an unidentified cylindrical object as he lay unconscious.

Lake, 52, and formerly of Hill Head, Glastonbury, was convicted of causing grievous bodily harm with intent, assault by penetration and criminal damage by a jury at Exeter Crown Court in February.

He was jailed for life by Judge David Evans and will not be released unless it is considered safe to do so. He must serve seven-and-a-half years before he can apply for parole.

The judge said a life sentence was the only way to protect the public because Lake suffers from an untreatable personality order with grandiose illusions, lacks empathy, and disregards social and sexual norms.

He told Lake: “The victim thought you were going to kill him. This assault was sadistic and cruelly targeted at a particular part of his body. You used alcohol to facilitate the offence and there was a significant degree of planning.

“He is suffering ongoing effects. The victim impact statements from him and his daughter show he is an entirely changed man, both physically and mentally, as a result of his experience at your hands.

“The circumstances of this and the previous offence shows a danger arising from invasive attacks on people’s bodies.

“The likely level of danger you pose to the public is very high with no discernible prospect of change.”

The victim made an impact statement which said he suffered excruciating pain for weeks after the attack because of a broken bone at the base of his spine and the injuries to his anus.

He struggled to carry on working and suffered nightmares and flashbacks that woke him repeatedly in the night.

Warren Robinson, defending, said Lake would have more incentive to respond to treatment while in jail if he had the prospect of release.

He said that psychiatric reports had diagnosed a personality disorder rather than a treatable mental illness, but this still reduced Lake’s culpability for the attack.

Lake did not give evidence at his trial but claimed he left the shop before the assault took place. He demanded to be addressed as Dr Lake at previous hearings because he holds an academic doctorate.