An inmate mounting a protest at Strangeways prison daubed 'FREE IPPZ' across the roof of the jail, in an apparent dig at a now abolished court sanction titled Imprisonment for Public Protection sentences (IPP).
The prisoner was also heard repeatedly shouting 'free IPPs'.
So what are IPPs, why were they scrapped and why does it remain an issue today?
READ MORE: LIVE: Prisoner spotted on roof of Strangeways prison - latest updates
In 2005, the then Home Secretary David Blunkett introduced Imprisonment for Public Protection sentences (IPP). The public, press and even some judges - confronted with this new tool - struggled to understand them at first.
Those who got them were handed minimum terms, often only of a few years, after which they had to convince the Parole Board they were safe to be released.
If they weren't deemed safe, they remained behind bars.
The problem was IPP prisoners weren't given access to courses so they could prove they were rehabilitated.
So they lost hope and many of them kicked off behind bars.
Your average prisoner serves half their sentence. But an IPP prisoner who was sentenced for a relatively minor crime could be forced to remain behind bars far longer than many killers, rapists, major drug dealers, paedophiles and organised criminals.
In 2012 IPPs were abolished on the back of a European Court ruling that they breached human rights - on the grounds that prisons had failed to provide inmates access to the rehabilitation courses required to demonstrate to the Parole Board that they were safe to be released.
But the abolition wasn't retrospective, so by 2019 there remained 2,489 prisoners still locked up on IPP sentences.
Among them was Wayne Bell who was just 17 when he was locked up for robbery in 2007 - he punched another lad and took his bike in Ladybarn Park in south Manchester.
It was his misfortune that he was among the first convicts to be handed the new type of sentence - since discredited and abolished as 'unjust'.
Every two years he went before the parole board but each time he was turned down amid continuing concerns about whether he was safe to be released. His probation officer also thought he wasn't safe to be released, according to his family.
There are others.
Within two years of their introduction, 3,000 people were handed IPPs - far more than had been anticipated by the Home Office.
Judges were often obliged to hand down such sentences if the person in the dock had committed one of 153 specified violent or sexual offences and if they had committed one previous specified offence. Judges could only depart from this in rare cases.
The Howard League, which campaigns for prison reform, concluded in 2013 that IPPs were 'poorly planned and implemented and resulted in unjust punishments, particularly those sentenced prior to 2008'. It urged the government to review IPP prisoners who remained behind bars.
It surveyed 103 senior prison governors and the vast majority reported IPPs had a negative impact on both prisoners and staff, in part because they didn't have the resources available to run rehabilitation courses required to demonstrate that inmates were safe to be released.
The parole board struggled to hear the increased number of hearings.
The prison population rose significantly.
The IPP was finally abolished in 2012 with the then Justice Secretary Ken Clarke stating the sentence had been 'inconsistent', used far more than intended and had proved 'unjust' for many recipients.
In 2017, Parole Board chairman Nick Hardwick told the justice committee of the House of Commons that IPP offenders were being released but that more than half were being recalled, sometimes only for minor breaches of the terms of their release.
Although long gone, IPPs remain a shameful blot on the landscape of our criminal justice system.
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