In the early years of the investigation, teams navigated practical and technological challenges.
On a visit to the archive in 2016, the BBC saw original police notebooks kept for 25 years in a lock-up.
Some were so neglected they had to be cleaned of rat droppings before they could be analysed.
Evidence on VHS tapes and floppy disks required resurrected 1980s computers to view and modern facial-recognition tools had to be used to track fans’ movements frame by frame.
The scale was unprecedented and there was a sense of purpose. Yet, 13 years on, the optimism felt by survivors and families has ebbed away.
After the criminal trials ended without significant convictions and after the police commander David Duckenfield was acquitted, many bereaved relatives began to lose faith in the process.
Several told the BBC they felt there was no point to the IOPC investigation.
They knew that all of the police officers involved had either retired or died. Even if they were found to be guilty of misconduct, no sanction could be imposed.
“I hope it’s not going to be a waste of taxpayers’ money,” Ms Hicks said.
“We’ve just had the Budget and people are struggling. Perhaps the money would have been better spent on the NHS, or somewhere else it’s desperately needed.”