A prison cell designed to be safe for a vulnerable inmate, who later hanged himself, was not fit for purpose, a former prison governor said.
The jury at the inquest of Michael Bailey, who died at privately-run HMP Rye Hill, near Daventry, in 2005, heard the "safer" cell in the prison's segregation unit should have prevented suicide by hanging.
Ron Tasker, who investigates deaths in custody, said prison staff had left a rivet hole in the door to Mr Bailey's cell, which he used to hang himself after his mental health rapidly deteriorated.
Mr Tasker, a former prison governor with 41 years' experience, said: "Cell 21 was a safer cell designed to be more safe than many cells in the system so you can't just tinker about with it.
"Everything would be flattened so you couldn't hang a coat hanger, shoe lace or anything on it.
"Rye Hill's cells were designed so the opportunity for people to hurt themselves would be much lower than other cells.
"They have put a rivet in it or they have intended to put a rivet in and that's the sort of tinkering about with stuff that you just can't do."
Jurors saw photographs of Mr Bailey's cell door where the observation panel had been coming loose, which prompted staff to put the rivet hole in the door to secure the metal plate.
Mr Tasker dismissed suggestions that Mr Bailey was a victim of racism in the prison but said inexperience had caused the staff to "back off" when disciplining him.
The inquest also heard from Michelle Green, now head of offending management at Rye Hill, who was the prison custody officer who found Mr Bailey in his cell on March 24, 2005.
She told the assistant deputy coroner, Tom Osborne, that Mr Bailey had not been checked by prison staff for at least half an hour despite records subsequently showing he had been.
The inquest was adjourned until next week.