Four men have been jailed for trying to smuggle cocaine worth more than £41m into the UK on a private jet from Colombia.

In one of the largest drug busts of its kind, the men, who had posed as “leaders in the field of cryptocurrency”, were stopped at Farnborough airport in Hampshire with half a tonne of cocaine in 15 suitcases after flying from Bogotá.

Martin Neil, 49, of Poole in Dorset, Italian national Alessandro Iembo, 28, and Spaniards Victor Franco-Lorenzo, 40, and José Ramón Miguélez-Botas, 56, were found guilty by a jury at Woolwich crown court in south-east London on Thursday.

They were each convicted of one count of fraudulent evasion of a prohibition in relation to a class A controlled drug, between 30 October and 30 January.

Martin Neil, who received a 24-year sentence. Photograph: National Crime Agency/PA

Neil’s brother Stephen Neil, 53, also of Poole, was found not guilty of the same charge after the jury deliberated for more than 13 hours.

Martin Neil, Iembo and Franco-Lorenzo, all from Bournemouth, received 24 years each, while Migueléz-Botas, of Valladolid in Spain, was given 20 years.

Border officials discovered the stash on 29 January, three days after the men left Luton heading for Colombia on a private jet costing £138,500.

A woman who gave her name as Claire Harris contacted Diamonté Jets and paid for the aircraft in cash. When the men returned, officials searched beyond a few dirty clothes in their suitcases to find 513 blocks of cocaine with a purity of about 79%.

The total weight of the drugs was about 500kg (1,100lb). Each individually wrapped block was embossed with branding used by Colombian cartels, such as the Superman emblem, and several packages had an “Esco” logo in a possible nod to Pablo Escobar, the notorious Colombian drug lord.

The wholesale value was £15.4m but the cocaine could have been sold for more than £41m on the street, the prosecution said, with a profit of more than £15m.

Police believe the operation may have been successful once before in December 2017, when Iembo, Martin Neil and Franco-Lorenzo made a three-day trip to Bogotá. A woman had again booked a private jet, then under the guise of the men being cryptocurrency experts who would be meeting the American singer Bruno Mars in Colombia as part of their work.

A chauffeur-driven Rolls-Royce Phantom was arranged to collect them when they returned to Farnborough on 11 December. They brought back a number of suitcases on that trip, but none were searched.

Police believe the men were pawns used by a wider network, and the woman, believed to be an associate of the network, remains at large.

Lawyers for the Neils said the pair had been “deceived”, believing they were visiting Colombia to help with charity work.

Celebrating the bust in January, Siobhan Micklethwaite, the National Crime Agency operations manager, said it was “one of the largest flown into the UK by plane in many years”.

Investigators conceded they had no leads on who directed the group, with a sophisticated encrypted phone used by Iembo being the only potential link.

Sentencing the men, Judge Philip Shorrock said the “serious and commercial operation” nearly succeeded in bringing an enormous haul of the class A drug into Britain.

He conceded they were not the masterminds, but all played a crucial part and hoped walk away with a substantial amount of money.

The NCA believes plotters carefully selected Farnborough over major hubs such as Heathrow and Gatwick because it is a small airfield.

There are about 3,000 smaller airstrips in the UK, many of which do not have full-time customs officers or police on site.

Steve McIntyre, a senior investigations manager at the NCA, said: “[Farnborough] does have border staff present on a daily basis, but it will never have the amount of business you will get at a major airport.

“That is a border vulnerability that we will have to try and tackle.”

CCTV of suitcases being unloaded from the executive jet at Farnborough Airport following the flight from Colombia. Photograph: National Crime Agency/PA

Ryan Willmott, a Border Force official based at Farnborough, said the smugglers made little effort to hide the drugs during the “ballsy” mission.

“Everyone always says to me, ‘How was it concealed?’ Nothing was concealed,” Willmott said. “There was random clothing sitting there but they didn’t attempt to conceal anything at all.”

Staff took the bags into their office for a search, accompanied by Iembo, who was forced to watch as his plot quickly unravelled.

“It was audacious, the way they went about their business,” McIntyre said. “We surmise they got away with it in 2017 and thought they were on for another win.”

Colombian authorities have arrested five further suspects in connection with the conspiracy.