Four leading health experts who charged the NHS £1.1 million while moonlighting privately have been jailed.
Basildon Hospital employed the group to provide heart and lung services but they only worked about half of their contracted hours, instead offering their services to other hospitals.
A court heard they showed a "cynical disregard" for NHS funding - referring to the hospital as "Bas Vegas" as they sought to cash in.
Judge David Owen-Jones described the scam as "a systemic, well-planned, organised and executed initiative".
He added: "While taking a salary from the NHS for a 37-and-a-half hour week, you worked elsewhere at other hospitals during NHS hours.
"You all four gravely abused the trust placed in you.
"It's awful to see people of your education, previous good character and achievements convicted of these kinds.
"I feel these offences were motivated purely by greed."
Martin Oliver, 37, Ann Clements, 51, John Mulholland, 41, and Tom Cumberland, 42, were convicted of conspiracy to defraud at Basildon Crown Court following a three-month trial.
Between 2007 and 2011, the four - directors of London-based private firm London Perfusion Science Ltd (LPS) - were contracted to provide clinical perfusion services to manage heart and lung machines during cardiac surgery at Basildon.
Over four years, the group failed to work 14,000 hours which they were paid for.
Instead, they earned an extra £700,000 for the company through their private work, largely at Hammersmith Hospital.
Prosecutor Shane Collery told the court Mulholland, an internationally renowned heart specialist, was the ring-leader.
As well as not working their own hours, they diverted more junior staff to work at other hospitals.
The court heard it was not clear exactly how much they profited from the scam, it is thought they earned salary overpayments totalling £420,000.
Emails read to the trial revealed their "cynical disregard" for NHS work, Mr Collery said.
They referred to the hospital as "Bas Vegas" - a nickname stemming from the US gambling capital Las Vegas.
One, sent by Mulholland to other defendants, revealed he tried to avoid NHS work "unless it's going to make cash/make our lives easier".
Benjamin Summers, mitigating for Mullholland, said the destruction of his career had been "utter and complete".
He had been forced to stand down from several international roles and was likely to lose his professional accreditation.
He added that Mullholland had a daughter with a serious long-term illness and his wife would be left as sole carer while he served a jail term.
It was said in mitigation for Clements, Oliver and Cumberland, that they were all medium-scale players whose careers were also in tatters.
Adam Kane, for Oliver, pointed out that no patients had suffered as a result of the fraud.
Mullholland, of Copenhagen Place, London, was jailed for three years.
Martin Oliver, of Basin Approach, East London; Ann Clements, of Wharf Lane, Limehouse, and Tom Cumberland, of Penge, London, were each jailed for two years.
All were banned from working as company directors for four years.
After the hearing Sue Frith, head of the National Investigation Service at NHS Protect, said: "From day one, John Mulholland and his associates set out to defraud the NHS of hundreds of thousands of pounds.
"The time, effort and planning that they were willing to put in to their criminal activities reaped them considerable rewards - until NHS Protect caught up with them.
"These custodial sentences reflect the seriousness of the offences and will act as a powerful deterrent to others."