A relative of Nye Bevan, the founder of the NHS, died after serious mistakes by two hospital trusts meant his lung cancer went from treatable to incurable, the Guardian can reveal.

Roderick Bevan would have survived but for the failure of two sets of doctors to tell him for more than a year that he had the disease, blunders that amounted to “neglect”, a coroner has ruled.

The deceased was a great-nephew of the health minister in the postwar Labour government who is widely revered for his role in driving through the creation of the health service in 1948.

Roderick Bevan died in May 2018 after NHS doctors diagnosed his lung cancer after a scan but did not ensure that he then underwent stereotactic ablative radiotherapy – treatment that if he had had it at the time was expected to cure him. The retired caretaker, who lived in Grantham in Lincolnshire, was 66 when he died. A catalogue of blunders meant that he was never offered the radiotherapy.

Bevan’s condition was first diagnosed in October 2016 by a lung cancer multi-disciplinary team (MDT) from the United Lincolnshire trust after he had a positron emission tomography (PET) scan at Pilgrim hospital in Boston, Lincolnshire, where he was already being treated for an abdominal aortic aneurysm.

However, neither doctors from there nor from the University Hospitals Leicester trust, to where his care was transferred, told him he had lung cancer until January last year – 15 months later – by which time the NHS could no longer save his life. It emerged at the inquest into his death that medical staff at both trusts had a series of opportunities to break the news to him during those 15 months, when he attended appointments for the aneurysm, but did not do so.

“I feel that my dad was totally let down by the NHS, whose founder was Nye Bevan who, as the name suggests, my dad was related to – it was his great uncle. I am sure that he would be appalled by the events that have unfolded,” said Roderick Bevan’s daughter, Paula.

At the end of the two-day inquest into the events surrounding his death that opened at Boston coroner’s court on 30 April and ended on 1 May, the coroner, Paul Smith, ruled that Roderick Bevan’s death was the result of “natural causes contributed to by neglect”.

In his verdict, the coroner said: “On the balance of probabilities, had the results of the PET scan and/or the recommendation of the multi-disciplinary team meeting of 11 October 2016 been acted upon promptly, the treatment proposed for Mr Bevan would have been successful.”

In the days before he died, Bevan asked his daughter to request an inquest into the care and treatment he received so that the mistakes in his case became known to the public in order to avoid others suffering as a result of the same errors.

Peter Walsh, the chief executive of Action against Medical Accidents, a charity that campaigns against medical negligence, said: “This is a shocking case of multiple failures by the NHS which appear to have taken away Mr Bevan’s chances of a cure.

“It is highly ironic that this should happen to a relative of Nye Bevan’s. However, this is not a novelty. Rather it is yet another example of how the modern-day NHS is failing far too many patients.

“Nye Bevan would turn in his grave if he knew the number of avoidable deaths and other serious harm being caused by failure in patient safety.”

Christine Bowerman of JMP Solicitors, which represented Bevan’s family at the inquest, said Bevan had died avoidably and prematurely as a direct result of “gross medical failings” and “numerous systematic errors” by the two trusts.

“This case was truly appalling, the fact that multiple individuals within two NHS trusts didn’t communicate to a patient in their care that he had a treatable lung cancer for 15 months is despicable”, said Bowerman, a specialist in medical negligence.

In his ruling, the coroner also noted: “His [Bevan’s] case was further considered by an MDT meeting in Leicester on 11 November 2016. A diagnosis of lung cancer was confirmed and it was recorded that he was likely to be eligible for a curative stereotactic ablative radiotherapy procedure. The PET scan result was sent to the referring consultant but not acted upon.”

Rachel Young, counsel for Bevan’s family, added: “The finding that death was by natural causes contributed to by neglect was the best that we could have hoped for from an inquest and it did reflect the fact that Mr Bevan’s death could certainly have been avoided.”

Dr Neill Hepburn, the medical director at the Lincolnshire trust, said: “We would like to offer our sincere condolences to the family of Mr Bevan.

“We accept that there were opportunities for us to communicate more effectively with Mr Bevan and have carried out a full investigation into the circumstances of his death. We have learned from this and have reviewed our practices and procedures.”

Dr Andrew Furlong, his counterpart at the Leicester trust, said: “Unfortunately Mr Bevan died in tragic circumstances; for that we remain incredibly sorry.”

Since looking into his death, the trust has changed its systems to prevent anything similar happening again. As a result, any patient with suspected cancer is included on a daily list seen by key doctors and managers across the trust, who then ensure investigations, treatment plans and the right care are arranged and tracked to see they occur, Furlong explained.