We recently featured a tieless Dan Hannan in action in the European Parliament but his open neck casual look would be against the rules in the House of Commons.
The Telegraph reports that Labour MP Graham Allen "was criticised by Sir Alan Haselhurst, the Deputy Speaker, because although he was wearing a suit, his shirt collar was open with no tie.":
"Sir Alan told the MP: "It is not appropriate to address the House without being properly attired." It is traditional for men to dress formally in the Chamber. Erskine May, the Parliamentary ‘bible’, states: "It is the custom for gentlemen members to wear jackets and ties.""