Harriet Walter’s acclaimed portrayal is the latest of many screen versions. So how do you create the Thatcher persona?

Harriet Walter has become the ­latest in a line of actors, from Meryl Streep and Gillian Anderson to Fenella Woolgar and Jennifer Saunders, to accept the challenge of becoming Margaret Thatcher on screen. How do you play a woman who, 45 years on from her ascension, exists almost as a national caricature?

Walter plays the part in Brian and Maggie, Channel 4’s two-part drama tracing Thatcher’s relationship with Labour MP turned journalist Brian Walden, which culminated in a fraught TV interview in October 1989, as Thatcher’s fortune began to fail. The series, written by Sherwood creator James Graham, directed by Stephen Frears and co-starring Steve Coogan, digs into the former prime minister’s private persona.