Early on in Michael Samuels’ unremittingly sombre film about Winnie Mandela, the star-crossed heroine made the observation that being married to Nelson meant you were also married to “the struggle”, and would inevitably end up in Nelson’s shadow. So it proved. Even as she went to meet Nelson (David Harewood) as he was finally released after 27 years in jail, Winnie (Sophie Okonedo) was advised to learn from the example of Prince Philip and the way he walks dutifully one step behind the Queen.