He was assessed by mental health professionals and was "not considered to be actively suicidal", the coroner said, but prison officers checked him frequently because of statements he had made about dying.
Over the following months he was moved several times in and out of the Intervention and Support Unit.
Prison officers who dealt with Pay over his last few weeks informed the Prison Inspectorate that they saw no indication that he was considering self-harm.
Nor did a prisoner who had spent time with him in his last few days, including just before the prison lock-up on the afternoon of his final day alive.
The coroner said that Pay suffered from multiple sclerosis which affected his mobility and balance, and chronic pain which interfered with his sleep.
Pay complained of pain and exhaustion throughout his time in prison. He had good days and bad days.
Sometimes he was able to walk independently in his unit; on others he was unable to get out of bed and prison officers would give his meals to him there.
"While only Mr Pay knows the specific reasons for his decision (to end his life), it can be inferred … that he found it intolerable to continue living with his medical condition and the chronic pain," Coroner Ryan said.
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