formal attire or black tie optional

U.K. Government Accused of Using EU Migrants as ‘Bargaining Chips’ formal attire or black tie optional Osborne To Slash Corporation Tax To Show U.K. is 'Still Open For Business' formal attire or black tie optional Chilcot Report: U.S. 'Pushed Britain Into Iraq War,' Says Former Ambassador to U.N. formal attire or black tie optional Britain’s Bank Shares Pummeled After Brexit Shockwave formal attire or black tie optional