A black prisoner with mental health difficulties died after being restrained by guards and his pleas that he could not breathe were ignored, an inquest has heard.
Wayne Bayley, 43, died on May 17, 2022, six days after he had been remanded to HMP Pentonville in north London.
An inquest heard he complained on the day of his death that his new cell was unclean, and guards decided he had to be restrained before being moved to a segregation unit.
The health of Mr Bayley, who had sickle cell disease, a delusional disorder, and epilepsy, began to deteriorate after he was restrained, and he repeatedly told prison workers that he was struggling to breathe.
A jury at Bow coroner's court concluded that Mr Bayley's death ten hours later was contributed to by neglect.
"In the two-and-a-half years since Wayne passed, we have lived with the knowledge that Wayne spent much of his last day not believed, naked, alone, unwell and without any medical treatment, despite having well-documented serious chronic health conditions", said his family.
"Restraint by prison officers caused Wayne to suffer a sickle cell crisis which he would have survived if he had received the most basic care.
"We very much hope that lessons learned from Wayne's death lead to meaningful changes in the way that vulnerable people with long term health conditions are cared for whilst in prison, both generally but particularly in circumstances involving restraint, so that others do not have to experience the pain of knowing their love one's death could have been so easily avoided."
The inquest was told Mr Bayley collapsed as he was being transferred to the segregation unit, and when he said he could not breathe he was subjected to a forcible strip search - with his clothes being cut off - instead of being rushed for medical care.
In segregation, a nurse failed to spot that Mr Bayley was in sickle cell crisis, his health was failing markedly, and vital observations were not taken.
His medical records - showing his sickle cell disease - were not checked before a referral was made for him for be assessed by a mental health nurse.
After seven hours in segregation, Mr Bayley was moved to the healthcare unit and collapsed again on the transfer, needing a wheelchair to complete the journey.
Hickman & Rose, solicitors for Mr Bayley's family, said he asked to see a doctor and repeated that he could not breathe, but vital observations were again not taken and he was provided with no further care.
Three hours later, he was found unresponsive and and died shortly before midnight.
The inquest jury found the lack of responses from Mr Bayley had been interpreted as non-compliance instead of signs of a medical emergency, there had been a breakdown of communication between prison and healthcare staff, and his condition had not been properly monitored in his final hours.
Ellie Cornish, from Hickman & Rose, said Mr Bayley's treatment had been "characterised by a profound lack of professional curiosity, common sense and humanity".
"Warning signs of what was in fact a medical emergency were disregarded, unnoticed or unidentified", she added.
"A sickle cell crisis can be entirely treatable but, as the jury found, multiple failures by prison and healthcare meant that, in this instance, it proved fatal.
"Wayne's family have shown extraordinary dignity and resilience throughout his inquest and the damning conclusion that his death was contributed to by neglect is an important step forward in their ongoing pursuit of justice for Wayne."
The Prisons Ombudsman previous investigated Mr Bayley's death and found a litany of failings.
It concluded the initial use of force on Mr Bayley was "not justified", the nurse who saw him had failed to monitor him properly, and staff had failed to investigate if he had sick cell disease.
There were delays in the healthcare he did receive, and there had been failures to consider his mental health issues.
The Ombudsman found Mr Bayley's request to see a doctor "was not properly explored or followed up", and it found that his cell - about which he had complained leading to the use of force - was "not fit for occupation".
Coroner Mary Hassell has now issued a report aimed at preventing future deaths in prisons.
She said lessons had been learned from Mr Bayley's death within Pentonville, particularly by those providing medical care for inmates.
"This work has covered the assessment, treatment and medication of all prisoners, from healthcare planning on arrival in prison, through any control and restraint, to the entering of a cell in an emergency, all particularly in the context of any underlying health conditions - including, but not limited to, giving staff a proper understanding of the identification of and risks associated with an acute sickle cell crisis", she said.
But she added that it is "not at all clear that this work has been replicated nationally".
She noted that more than half of the prisons in England and Wales are served by a different healthcare provider to Pentonville, and added: "Learning and improvements in practice may not have been shared across the country."
A Prison Service spokesperson said: "Our thoughts are with Mr Bayley's family and friends at this difficult time.
"Following Mr Bayley's death, we have improved training for prison staff around the use of force and segregation to ensure that prisoners and prison staff are kept safe. We will respond to the Prevention of Future Deaths report in due course."