The UK's highest court rules today on an action by two high-profile terrorist prisoners who claim their human rights were violated when they were segregated for extended periods.
Five Supreme Court justices in London will announce their decision on challenges brought by Ricin plot conspirator Kamel Bourgass and ''liquid bomber'' Tanvir Hussain.
In March 2012 the pair failed to persuade appeal judges that their treatment was unlawful.
They were alleged to have intimidated and bullied other inmates over matters of faith, and authorities in their respective jails had considered it was necessary to separate them from other prisoners ''for good order and discipline''.
Both men denied accusations that they tried to influence and dictate the beliefs of other prisoners.
Their QC Dinah Rose told the Supreme Court at a hearing in February: "The issue in these appeals is one of fairness.
"Fairness requires that prisoners should be provided with sufficient information about the reasons and evidence relied on to justify the initial decision to segregate them, and their continuing segregation, so as to enable them to make meaningful and effective representations in their defence.
"Fairness also requires that, at least once it is apparent that the segregation is not simply a short-term measure, prisoners should be afforded the opportunity to challenge the decision to segregate them before a body that is independent of the prison, and which is empowered to determine whether the factual case against them is made out and whether their continued segregation is justified."
Bourgass, an Algerian, is serving 17 years for conspiracy to commit public nuisance by using poisons or explosives in relation to the 2002 Ricin terrorist plot.
He is also serving a life sentence for murdering Detective Constable Stephen Oake, 40, with a kitchen knife during his 2003 arrest at a flat in Manchester.
He injured four other officers during that attack and is serving sentences for attempted murder of two officers and wounding a third.
Hussain was one of three men convicted of a plot to launch suicide attacks on flights from Heathrow to America and Canada using liquid bombs made of hydrogen peroxide hidden in soft drink bottles. He is serving life with a minimum tariff of 32 years.
While detained at HMP Whitemoor in Cambridgeshire, Bourgass was segregated from March 10 2010 until April 22 and again from April 23 until October or November of that year. Hussain was segregated at HMP Frankland in County Durham from April 24 2010 until October 2010.
Ms Rose told Supreme Court president Lord Neuberger, Lady Hale and Lords Sumption, Reed and Hodge that neither man was provided with adequate reasons or information concerning the evidence relied on to justify their initial or continued segregation.
They were "not informed of what they were required to do in order for their segregation to end, and were not afforded the opportunity to challenge the relevant decisions before an independent body".
She argued that "in the circumstances", the decisions to segregate them and to continue that segregation were "unlawful".
Ms Rose told the court: "In each case there was said to be a suspicion that the appellants had been involved in assaults on other prisoners.
"In neither case was there sufficient evidence to bring criminal charges or sustain internal prison disciplinary charges against them."
Both men, she said, were held in segregation in different prisons for approximately six months and during that time they were locked alone in a cell for 23 hours a day and permitted only one hour of exercise a day, "which had to be taken alone in a cage".
The QC submitted that there were a number of reasons why "stringent standards of fairness must be applied", including the serious effects of segregation on prisoners, particularly when it was prolonged.
"It is accepted that segregation carries a high risk of deterioration in mental health, and that after the segregation has continued for a period in excess of two weeks there is a risk of irreparable damage to the prisoner," she said.
Back in February 2011 a High Court judge said the procedures adopted to place them in, and keep them in, segregation did not breach their common law rights, or their rights under Article 6 of the European Convention on Human Rights to fair treatment.
In the Court of Appeal Lord Justice Maurice Kay said that in his judgment prison decision-making processes and the role of the Segregation Review Board (SRB) "provide a satisfactory framework for professional and evaluative judgments with the safeguard of judicial review".