It has long been the rule that foreign law is treated by the English Court as a question of fact which must be pleaded and proved. Proof of foreign law has traditionally been by way of expert evidence. As long ago as the Sussex Peerage Case(1844) 11 Cl & Fin 85, Lord Brougham said that “the judge has not organs to know and to deal with the text of the foreign law, and therefore requires the assistance of a lawyer who
knows how to interpret it”.
That orthodoxy, and Lord Brougham’s restricted view of an English judge’s ability to interpret foreign law without expert evidence, has been questioned by Lord Leggatt in Brownlie v FS Cairo (Nile Plaza) LLC  3 WLR 1011. When addressing the issue of how the Court should approach questions governed by foreign law where there is no adequate proof of that foreign law before the English Court, Lord Leggatt also turned his focus on the means by which litigants can prove foreign law.
For the full piece, produced by Giles Wheeler KC, please see here.