Which murder-mystery play has been running in the West End since 1952?

Which of these was a British invention in the 20th century? Practise question Can the public listen to debates in both the House of Commons and the House of Lords? Practise question In Northern Ireland, must a newly qualified driver display an R plate for one year? Practise question What did the first coins minted in Britain during the Iron Age feature? Practise question In what year was the Women's Franchise League established by Emmeline Pankhurst? Practise question How are parliamentary proceedings made publicly accessible? Practise question Who lost power after the Battle of Culloden? Practise question Who was Richard Austen Butler? Practise question When was the Battle of Agincourt fought? Practise question