The Supreme Court, the highest court in the UK, was the Appellate Committee of the House of Lords until 2009. It is now housed in the neo-Gothic Middlesex Guildhall (1913) on Parliament Sq. There's a permanent exhibition looking at the work and history of the UK’s highest court as well as the building's history on the lower-ground floor. The self-guided tour booklet is £1; tours are also available on Fridays (£5; 11am, 2pm and 3pm).
During the Supreme Court's summer recess, there are further tours at 11am and 2pm on most weekdays during August and early September. Members of the public are welcome to observe cases when the court is sitting (Monday to Thursday). For who or what's on trial, ask for a list at reception, or go to the Current Cases page of the court's website.