Private landlord, Salah Ali, 52, of Wembley, has been fined a record £1.4m after converting a house in Willesden Lane, north-west London, into 12 flats without planning permission.
If he does not pay within 6 months, Ali has been warned that he could face a jail sentence of up to 10 years.
A judge at Norwich Crown Court ordered Ali to pay a fine of £4,000 for breaching planning regulations; legal costs of almost £35,000; and a confiscation order of £1.438m.
He was also issued with a restraint order which prevents him from disposing of his assets before paying the fine.
Brent Council will receive around £500,000 (37.5%) of the confiscation order. The remaining 62.5% will go to the Treasury and the court collection agency.
The council said the £1.438m order, made using powers available to local authorities to recover the proceeds of crime, is believed to be the highest confiscation order for a planning offence anywhere in the country.
The figure was based on estimations of the rent that Ali is understood to have received from tenants living in the property.
Chris Walker, Brent Council’s assistant director of planning, said: “This landlord ignored planning rules designed to ensure that the quality of accommodation in the borough is maintained and that the environment for surrounding residents is protected. He ignored the council’s notices, and as a result he profited hugely from this sub-standard accommodation.”