A wealthy businessman has agreed to hand over nearly £10m of assets, including dozens of properties across England, after investigators accused him of being a money launderer for major crimelords in the north of England.

Mansoor Hussain, 40, a property developer from Leeds, was hit with an “unexplained wealth order” by the National Crime Agency (NCA), which compelled him to provide evidence of the source of his wealth.

Hussain, known as Manni, agreed to hand over nearly £10m worth of properties, land and cash in an out-of-court settlement after the NCA confronted him with the evidence it had accrued. A finding against him in a high court trial could have resulted in a more severe penalty.

Hussain seen in a photo from his social media with Meghan Markle, now the Duchess of Sussex. Photograph: Twitter

This is the first time an unexplained wealth order has successfully led to the recovery of assets from an individual. They have been used in four cases, including Hussain’s. Two are ongoing and one was rejected by the courts.

Hussain represented himself in talks with the NCA. The settlement was agreed on 24 August, and the high court sealed the recovery order on 2 October 2020.

The UWO process is administered under civil law, which has a lower threshold for standard of proof than criminal law. The NCA said they were unable to mount a case against Hussain in the criminal courts. He has no criminal convictions.

The investigators alleged Hussain had links to a gang in the Bradford area operated by the Khan family, headed by Mohammed Nisar Khan, known locally as “Meggy”, who was jailed for 26 years in 2019 for murder, and an organised crime gang operated across the north of England run by notorious gangster and convicted armed robber Dennis Slade.

Graeme Biggar, director general of the National Economic Crime Centre, NCA, said: “This case is a milestone, demonstrating the power of unexplained wealth orders, with significant implications for how we pursue illicit finance in the UK.

“This groundbreaking investigation has recovered millions of pounds worth of criminally obtained property. It is crucial for the economic health of local communities such as Leeds, and for the country as a whole, that we ensure property and other assets are held legitimately.”

Image issued by the National Crime Agency of 2 Sandmoor Drive, Leeds, one of the properties seized through an unexplained wealth order. Photograph: NCA/PA

Andy Lewis, NCA head of civil recovery, said: “He had a huge number of properties, he led a good lifestyle. But that’s now come to an end, now we’ve taken away vast majority,” Lewis said.

The NCA was investigating organised crime in the Leeds and Bradford area and they came to suspect Hussain of money laundering for the gangs.

On the face of it, he was businessman with no criminal convictions but strong associations with notorious criminals the area, Lewis said.

He had allowed Slade, a convicted armed robber, to stay rent free in his seven-bedroom house in Leeds, and later rent free in a penthouse apartment in Leeds.

Hussain seen with Beyoncé in a photo from his Facebook page. Photograph: Facebook

After Hussain was hit with the order, he complied, supplying a 76-page witness statement and about 127 arch lever files of documentary evidence.

However, Lewis said the evidence provided by Hussain actually bolstered the NCA case and investigators identified a larger property portfolio than was previously known. “Our case was it had all been financed by organised crime,” Lewis said.

Hussain had a large number of companies and bank accounts. The NCA used another power – an account freezing order – against him.

Lewis said the NCA was unable to launch a criminal prosecution because the “seed funding” for Hussain’s assets dated back nearly 20 years, which would have been too difficult to trace. He added it was best value for the taxpayer to pursue an out of court settlement, rather than proceed to a full high court trial.

He has ultimately handed over 45 properties in London, Cheshire and Leeds, four parcels of land, £600k in cash and other assets with a combined value of £9.8m.

Lewis said he had lost the majority of his assets, although he was left with four properties, which are “highly mortgaged”.

Biggar said criminal prosecution was always the preference but it is not always possible.

The Guardian contacted Hussain via his company Zarina Capital for comment.

• This article was amended on 2 November 2020. It is the standard of proof which has a lower threshold in civil law than criminal law, not the burden of proof as an earlier version said.