On Tuesday 24 September, the UK Supreme Court delivered an historic judgement, declaring Prime Minister Boris Johnson's suspension of parliament unlawful. With the ink on this extraordinary ruling barely dry, Professor Steve Peers, Professor Maurice Sunkin QC (Hon) and Dr Charilaos Nikolaidis discuss the issue of justiciability - whether the courts had the power to intervene - why the judges found Boris Johnson's prorogation unlawful and the implications in terms of Brexit, the UK Constitution and the interaction of judges, the executive and parliament.