Nigel Farage, the former Ukip leader's closest aide George Cottrell who runs Mr Farage’s private office, is in custody in the US awaiting trial on 21 charges including attempted extortion, money laundering and fraud after allegedly being caught in an FBI sting accused of offering to launder money for drug traffickers after advertising his services on the dark web.

The 22-year-old, whose former glamour model mother once dated Prince Charles, used the dark web websites that offer privacy because they are difficult to be traced and need special software called Tor to access.

But the ‘drug traffickers’ he is alleged to have dealt with were really undercover FBI agents.

Who is George Cottrell?

Cottrell who is the grandson of late Yorkshire landowner Lord Manton, was arrested last month as he and Mr Farage were returning from a series of engagements at the Republican Convention in Cleveland, Ohio.

To Mr Farage’s shock there were five FBI officers waiting to meet Cottrell as they disembarked from their return flight from Cleveland to Chicago O’Hare airport on July 22, en route to Heathrow. He was arrested and led away in handcuffs.

A trusted member of Mr Farage’s inner circle, Cottrell had just agreed to take on a permanent role organising the Ukip MEP’s diary and dealing with media inquiries.

His email accounts, which include details of many of Mr Farage’s day-to-day arrangements, have been frozen.

Advertised his money laundering services in the dark web

Court documents filed in the United States allege Mr Cottrell using the alias “Bill” was offering money laundering services on the dark web.

In 2014 he was contacted by FBI agents pretending to be “drug traffickers” where he promised to launder their cash for a fee in complete anonymity and security through his offshore accounts.

After meeting with the undercover agents in Las Vegas, Cottrell arranged for them to send him £15,500. He is alleged to have then attempted to blackmail the ‘drug traffickers’ by demanding £62,000 in the form of bitcoin the digital currency, saying he would alert the authorities if they refused.

A Ukip spokesman said:

“George was an unpaid and enthusiastic volunteer for the party over the period of the referendum. We are unaware of the details of the allegations excepting that they date from a time before he was directly involved in the party.”

The US District Court in Illinois remanded Cottrell in custody while criminal proceedings continue, ruling that he posed a “serious flight risk” with court documents claiming he had a “serious, years-long gambling problem, which inherently suggests a strong possibility of irrational risk taking.”