Between October 2014 and June last year the Dutch criminals trafficked narcotics packaged in colour-coded parcels in secret compartments in the emergency vehicles.
They made at least 45 trips, hiding Class A drugs inside the roof linings and under the floors of the ambulances.
The gang drove the lethal stashes from their native Amsterdam through ports at Harwich and Hull.
UK authorities thought they were collecting sick Dutch tourists; one member of the gang even brazenly posed as an injured holidaymaker – complete with a pair of crutches.
The UK gang then collected the drugs and sold them on UK streets.
The National Crime Agency (NCA) finally busted them after tracking an ambulance from Harwich to a scrapyard in Smethwick, West Mids, on June 16 last year.
Inside the ambulance officers found 193kg of cocaine and 74kg of heroin, 20,000 ecstasy tablets and 2kg of MDMA crystal.
The drugs were marked with different coloured tape alongside a matching list of 20 customers, including UK ringleader Gibson, of Cinder Lane, who had direct contact with the Dutch gangsters.
Judge Francis Laird QC said: “The events of June 16 triggered an investigation in the UK and the Netherlands.
“Two premises in the Netherlands linked with Schoon were searched and a fleet of ambulances were recovered.
“Eleven vehicles in total, of which four were modified to conceal drugs. Evidence from satellite navigation systems, mobile phone calls, and CCTV showed there were in total 45 trips to the UK by the Dutch ambulances.”
Two of the UK criminals – Raymond De Dilva and Petrit Kastrati – were arrested at the scene, and four more were caught from evidence gathered in the ambulance.
The three Dutch criminals – Olof Schoon, Leonardus Bijlsma, and Richard Engelsbel – were jailed for a total of 70 years in November last year.
Today, the six men from the British side of the operation were sentenced at Birmingham Crown Court for conspiracy to import and supply class A drugs across the UK.
Gibson, 56, of Ollerton, who was the “central player” in the plot, was jailed for 20 years for conspiracy to import the drugs.
He also received a concurrent 15-year sentence for conspiracy to supply and a three-year concurrent sentence for concealing criminal property on January 14.
Gibson’s right-hand man Darren Owen, 48, of Rushden, Northants, who would meet the ambulances on a weekly basis, was caged for 15 years for conspiracy to import the drugs.
Richard Clarke, 36, of Acton, Suffolk, who was in charge of storing the narcotics, received 11 years behind bars for conspiracy to supply drugs.
Jonathan Floyd, 47, of Burnage, Manchester – the gang’s northwest distributor – was handed a 15-year sentence for conspiracy to import drugs.
Raymond De Silva, 61, of Slough, Berkshire, a courier trusted to meet the ambulances five times by Gibson, was jailed for 16 years for conspiracy to import drugs.
Petrit Kastrati, 42, of Crystal Palace, London, a courier for a separate gang, was jailed for 17 years and six months for conspiracy to import drugs.
Judge Laird added: “This was a highly sophisticated, meticulously planned and well executed conspiracy to import Class A drugs on a truly colossal scale.
“Schoon’s cover was that these ambulances were transporting patients from the UK to the Netherlands, and on some occasions false patients were employed.
“Having heard evidence I’m satisfied that as a result of this conspiracy the wholesale value of the total number of drugs was no less than £300 million.
“Gibson, yours was an organisational role. You were towards the top of the tree.”
All of the UK defendants except Clarke were found guilty of conspiracy to import Class A drugs from October 1, 2014 to June 17 last year.
Gibson, Owen, Floyd and Clarke were found guilty of conspiracy to supply Class A drugs from January 1 to September last year.
Prosecutor Robert Davies said: “Schoon was running an ostensibly legitimate ambulance business in Holland.
“He had a fleet of paramedic vehicles including 11 ambulances. When examined in due course, four of these had been skillfully adapted to transport large quantities of Class A drugs.
“It was a fantastically convincing front for the real business, namely shipping drugs into the UK and elsewhere in Europe.
“Bogus paperwork was created for ‘patients’ that were to be collected in the UK and on some trips people were recruited to act as medically incapacitated passengers.”
Last November, Schoon was jailed for 24 years, Bijlsma was sentenced to 28 years and Englesbell was jailed for 18 years.