The widow of murdered Belfast solicitor Pat Finucane has said she is "quite optimistic" that the UK Supreme Court will see the "true facts" and rule in favour of a full public inquiry into her husband's death.
Mr Finucane was shot dead by loyalist paramilitaries at his north Belfast home in 1989 in front of his three children and his wife, Geraldine, who was also injured during the attack.
Speaking as she and her children arrived at the court, Geraldine Finucane said she wanted the court to decide that there should be an inquiry, saying it was a promise made to her and her family - and to the Irish Government - by the British government.
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She said governments should be held to account and not just change their minds when it suits them.
Asked what they would do if the latest bid for an inquiry failed, she vowed: "We will never stop."
Taoiseach Leo Varadkar has confirmed that the Government supports a public inquiry into the murder of Pat Finucane.
Responding to a question from Sinn Féin leader Mary Lou McDonald in the Dáil this afternoon, the Taoiseach said: "It is absolutely the Government's position that there should be a public inquiry into the killing of Pat Finucane.
He said Tánaiste Simon Coveney is due to meet with the family soon and it is something that they will continue to raise with the British government.
The Supreme Court will examine a number of issues including whether the failure to establish a full inquiry contravenes European human rights legalisation.
In 2011 the then British prime minister David Cameron commissioned a review of Mr Finucane's death.
The Finucane family dismissed the findings of the review as a whitewash and accused the British government of reneging on previous commitments to hold a full tribunal into allegations of state collusion in Mr Finucane's murder.
Mrs Finucane was granted permission in July 2017 to appeal to the Supreme Court against the decision of the Court of Appeal to hold a full inquiry.
A panel of five Supreme Court justices, headed by the court's president Lady Hale, will consider her appeal against that ruling during a two-day hearing.
Opening Mrs Finucane's case at the Supreme Court, Barry Macdonald QC said the background to the proceedings was "complex and sinister".
The case, he said, was "notorious for good reason", and was one which had attracted widespread local and international concern.
He added: "The available evidence suggests that agents of the state responsible for law enforcement devised and operated a policy of extra-judicial execution, the essential feature of which was that loyalist terrorist organisations were infiltrated, resourced and manipulated in order to murder individuals identified by state agents as suitable for assassination - in other words, a policy of 'murder by proxy' whereby the state itself engaged in terrorism through the agency of loyalist paramilitaries."
Mr Finucane, who enjoyed a reputation as a committed human rights lawyer prepared to challenge perceived abuses of state power "was a victim of this policy".
The QC said: "All investigations into Patrick Finucane's death have clearly established that he was no more than a solicitor intent on doing his job and doing it very well, albeit at the expense of attracting the adverse attention of elements of the state."
During the proceedings the justices will hear submissions from James Eadie QC on behalf of the Secretary of State for Northern Ireland.
In written argument before the court opposing the appeal, Mr Eadie submits that the lower courts which considered the case correctly concluded that the decision-making process relating to the public inquiry was a "thorough, genuine and lawful" one.
He said the Supreme Court was being invited to dismiss the appeal on the basis that decisions not to establish the inquiry "were lawful as a matter of public law", and that "no such obligation" could be derived from the Human Rights Act.
Additional Reporting PA