A psychotic cannabis user has been jailed for burning down his father’s home in revenge for him refusing to lend him money to invest in an online get-rich-quick scheme.

Jai Griffiths splashed the contents of a can of petrol over all the rooms in the house in Dartmouth before setting light to it and fleeing the resulting inferno.

The fire was so intense that it wrecked the house and smoke spread through a loft space into a neighbour’s house, where a 14-year-old girl had to flee into the street.

Griffiths was seen on CCTV filling the can at a filling station near his home before he returned there and started the fire on December 9 last year. His father Ian was out at work and came home to find it almost gutted.

His son was unemployed and had become a recluse who spent his benefits on cannabis and most of his time on the internet, where he had become convinced that a crypto currency scheme would make him a fortune.

He asked his father and other relatives to go to the bank and take out money for him to invest and threatened to burn the house down if they refused.

The fire put neighbours and firefighters at risk and led to an online appeal to help Griffith’s father, who was said to have ‘lost absolutely everything’.

Griffiths, aged 36, formerly of Davis Road, Dartmouth, admitted arson being reckless whether life was endangered and possession of cannabis. He was jailed for three years and four months by Recorder Mr Richard Paige at Exeter Crown Court.

He has been treated for paranoid schizophrenia at Langdon Hospital in Dawlish but the judge was told his psychotic condition was induced by his heavy use of cannabis, his condition has improved with treatment, and he is not considered suitable for a hospital order.

The judge told him: “You were upset that your father would not take you to the bank. You purchased petrol and poured it throughout the property before setting it alight. There was a significant risk of serious harm and not insignificant damage was caused.

“I make a downward adjustment to the sentence to take account of the impact of your mental health issues but note from the psychiatric report that it arises from your own abuse of cannabis.”

Mr Rowan Jenkins, prosecuting, said Griffiths had become obsessed with an online investment scheme and wanted his father and grandfather to take out money to join it. He messaged his grandmother the day before the fire to warn that he would burn the house down if they didn’t.

Nobody was hurt in the fire and the Guinness Trust, which rented it to Ian Griffiths, have not provided a figure of how much it has cost to repair. Police arrested Griffiths nearby with 64 ready rolled cannabis joints in his possession.

Mr Martin Salloway, defending, said Griffith’s actions were the result of his mental illness and him being heavily under the influence of cannabis.