The title of the Donmar’s new effort, Marys Seacole, appears to be a misprint and that makes the reader look twice. Good marketing. The show is a blend of Spike Milligan-esque sketches and indignant speeches about race but it starts as a straightforward historical narrative. Mary Seacole enters in Victorian garb and introduces herself as a woman of half-Scots and half-Caribbean heritage who believes that ethnic differences create hierarchies of competence.