Pawel Honc, Mariusz Tomaszewski, Oskar Pawlowicz, and Dawid Tychon took part in the raid at Paul Kohler's home
Four burglars who took part in a raid during which a lecturer was left "unrecognisable" have been jailed.
Paul Kohler, 55, needed facial reconstruction surgery after the attack in Kings Road, Wimbledon, on 11 August.
Mariusz Tomaszewski, 32, and Pawel Honc, 24, received 19 years each after admitting causing grievous bodily harm with intent and aggravated burglary.
Oskar Pawlowicz, 30, and Dawid Tychon, 29, who admitted aggravated burglary, were sentenced to 13 years each.
Judge Susan Tapping told Kingston Crown Court they had targeted Mr Kohler's south London home either because they were looking for items to steal or they chose the wrong address to collect a debt.
All of the defendants had been under the influence of drugs and alcohol on the day of the attack, the judge said.
In his witness statement, Mr Kohler called for the defendants to explain "the real reason" why his family was targeted.
Paul Kohler needed facial reconstruction surgery after the attack
Referring to the victim's request, the judge said: "Without this explanation he understandably questions the true value of any remorse expressed."
Honc, of no fixed address, Tomaszewski, of Crusoe Road, Mitcham, south London, Pawlowicz, of Pitcairn Road, Mitcham, and Tychon, of no fixed address, are all Polish nationals.
The court heard that, apart from Honc, all the other defendants had long criminal records in their home country, with 32 convictions between them.
Pawlowicz had also been convicted in the UK for offences including sexual assault and affray.
The court heard on the evening of the attack Mr Kohler answered the door while his wife Samantha MacArthur, daughter Eloise and her boyfriend Geraint were upstairs.
Mr Kohler, head of law at the School of Oriental and African Studies in London, was held down on the floor during the five-minute attack as one of the men sat on him and repeatedly punched him in the face while another kicked him in the head, the court heard.
The lecturer suffered a fractured eye socket, a fractured left jawbone, a broken nose and bruising that left him "utterly unrecognisable", the court heard.
Two of the men ran upstairs and confronted Ms MacArthur. The couple's daughter and her boyfriend were able to call the police after they hid in a bedroom.
Paul Kohler had asked the defendants to explain why they had targeted his family
Investigating officer Det Insp Dan O'Sullivan said the level of violence used was "utterly unnecessary" and the incident had a lasting effect on Mr Kohler and his family.
In his victim statement Mr Kohler also revealed the burglary had taken place a few months after he had suffered a heart attack and he had been left with permanent double vision as a result of the injuries he sustained in the raid.