Nearly 1.3 tonnes of heroin have been recovered by British authorities in the largest seizure of the class-A drug in the country, the National Crime Agency (NCA) revealed on Wednesday.

The haul would be worth around £27 million (€29.8 million) to criminals at wholesale but a whopping £120 million (€132.5 million) at street level, the NCA estimated in a statement.

The drug was recovered on August 30 after the MV Gibraltar container ship docked in the port of Felixstowe, in south-eastern England, en route to Antwerp in Belgium.

Officers from Britain's Border Force removed the 1,297 kg of drug concealed in towels and bathrobes, returned the container to the ship and let it continue its journey.

"The smugglers had hidden the drugs within a coverload of towels, stitching the 1kg blocks of heroin inside some of the towels. In total it took my officers nearly six hours — working in the early hours of Saturday morning — to remove the drugs," Jenny Sharp, Border Force Assistant Director at Felixstowe, explained.

Once in Antwerp, Dutch and Belgian law enforcement followed the container as it was driven by lorry to Rotterdam in the Netherlands before swooping in and arresting four people who were in the process of unloading the consignment.

"This is a record heroin seizure in the UK and one of the largest ever in Europe. It will have denied organised crime tens of millions of pounds in profits and is the result of a targeted, intelligence-led investigation, carried out by the NCA with international and UK partners" NCA Deputy Director Matt Horne said.

"The size of this and other recent shipments demonstrate the scale of the threat we face," he added.

Earlier in the month, UK authorities had also seized 398 kg of heroin in a vessel at Felixstowe port.