Dame Harriet Mary Walter DBE (born 24 September 1950) is a British stage and screen actress. Her film appearances include Sense and Sensibility (1995), The Governess (1998), Villa des Roses (2002), Atonement (2007) and Man Up (2015). On television she starred as Natalie Chandler in the ITV drama series Law & Order: UK (2009–14), as Lady Prudence Shackleton in four episodes of Downton Abbey (2013–15), as Clementine Churchill in The Crown (2016) and Lady Caroline Collingwood in Succession (2018-19). She was appointed Dame Commander of the Order of the British Empire (DBE) in 2011 for services to drama.