The cannabis addict who shot dead Sergeant Matt Ratana in a South London police station has been given a whole life order.

Louis De Zoysa purchased the gun in lockdown as he feared the pandemic would lead to food shortages and he would need to hunt wildlife to survive.

The 25-year-old, who has been diagnosed with Asperger’s Syndrome when he was younger, became obsessed with firearms after joining the cadets at school.

After buying an antique revolver in an online auction he manufactured his own ammunition in a rented garage in Banstead, Surrey and successfully made the decommissioned weapon viable.

De Zoysa later told a psychologist he believed the shops would run out of food during the coronavirus pandemic and he would need to kill deer and other wildlife in order to survive.

De Zoysa, who was a heavy cannabis user, also began carrying a gun after being robbed and beaten up in a drug deal gone wrong.

Following his arrest during a stop and search in September 2020, De Zoysa used the modified revolver to shoot and kill custody sergeant Matt Ratana, at Croydon police station.

Despite having his hands cuffed behind his back at the time, De Zoysa was able to remove the weapon which was hidden about his person, point it at the officer and fire two shots at his body.

As officers ran into the cell in order to restrain him he fired off two more shots, one of which severed his carotid artery causing a loss of blood to the brain tissue.

During emergency surgery, a section of his skull had to be removed to relieve the pressure and a metal plate was placed in the area.

He suffered a degree of paralysis in his right leg and requires the use of a wheelchair, as well as problems with speech and understanding.

Born in Croydon, De Zoysa was baptised a Catholic and had been a regular churchgoer in his youth.

Former school friends described De Zoysa as being bright but something of a loner who was socially very awkward.

After leaving school he won a place at University College London and later began working at Her Majesty’s Revenue and Customs. He also supplemented his income by investing in cryptocurrency.

De Zoysa admitted spending around £200 a month on extremely strong skunk cannabis and also said he would misuse the opiate codeine.

When his Banstead hideout was searched police discovered a pipe gun, a dummy launcher, an infantry rifle and various types of ammunition.

Electronic devices that were examined revealed an interest in weaponry and violence across a spectrum of ideologies including right-wing extremism and Islamic extremism.