Officials have seized a ship reportedly packed with £100 million of Libyan money and escorted her into a British port, the Home Office said today.
The vessel returned to UK waters after failing to dock in the Libyan capital Tripoli last weekend.
She was tracked by British authorities and intercepted off the UK coast, before being escorted into Harwich docks in Essex by the UK Border Agency boat HMC Vigilant.
A Home Office spokesman said: "A vessel which had been heading to Libya returned to the UK on Wednesday morning.
"The ship was escorted into the port of Harwich by the UK Border Agency cutter HMC Vigilant.
"A number of containers were offloaded from the boat and have been taken under control of UK Border Agency and have been moved to a secure location.
"The cargo is understood to contain a significant quantity of Libyan currency, which is subject to a UN sanction."
The Government imposed an export control order banning any Libyan currency leaving the country for the next year.
The dinar is printed in a warehouse in north-east England.
It is understood the unnamed ship failed to berth in Tripoli last weekend because her crew believed it was too dangerous.
Reports suggested the cargo ship was carrying £100 million worth of the Libyan currency, the dinar, but the Home Office refused to confirm the exact value.
They would also not disclose the name of the ship seized, or under which flag she was sailing.
Chancellor George Osborne froze Libyan leader Colonel Muammar Gaddafi's £900 million of UK-based assets on Sunday.
The UK also banned the unlicensed export of any uncirculated Libyan banknotes from Britain in line with UN sanctions.
There were thought to be 12 crew on board HMC Vigilant, an unarmed, 238-tonne patrol vessel, when she intercepted the ship.
Vigilant was built at Damen Shipyard in the Netherlands, launched in 2003 and cost £4.3 million.
She has three sister ships operated by the UK Border Agency in British waters - Seeker, Searcher and Valiant.
Last year Vigilant's crew seized 661lb (300kg) of cocaine off the Isle of Wight.