Despite the title, the main focus of Sebastian Barry’s new play, Andersen’s English, (co-produced with Out of Joint) is Charles Dickens’ treatment of Catherine, the fertile wife who bore him ten children before they separated at his insistence.

After a chance meeting in 1847 (and barely any contact in the intervening decade) Andersen, the famous Danish author of children’s fairytales, arrived at Dickens’ Kent home for a fortnight’s visit in the summer of 1857. He outstayed his welcome by several weeks, during which time he witnessed, though failed to register, a fracturing marriage and his host’s callous behaviour towards both his spouse and son.

Danny Sapani plays the visiting Dane as an enthusiastic and overgrown child, an outsider with extremely limited English, rigid habits and the eccentric habit of travelling with a length of rope in case fire necessitates a hasty escape. The (fictional) little Irish maid Aggie (Lisa Kerr) handles him with considerable tact, despite her own unfortunate predicament which will lead to her dismissal. And Max Stafford-Clark’s touring production overcomes the problem of so many children by casting puppets as the youngest youngsters.

Andersen’s presence doesn’t really add much insight to the portrayal of Catherine and Charles’ terminal relationship, which is by far the most interesting aspect of the play. Threatened as a mother by her husband’s decision to send her beloved son Wally off to join the army in India, and as a wife by the continued presence of her own younger sister Georgie, Niamh Cusack’s Catherine loses him to the much younger actress Ellen. It’s a touchingly sympathetic performance despite the fact that, physically, Cusack is nothing like the plump spouse specifically referred to in the text.

David Rintoul is imposing as Dickens (a public philanthropist revealed here as a tetchy, private bully)  but one leaves with the feeling that Barry has only scratched the surface of his characters and the events that shaped them.

Hampstead, Eton Avenue, NW3 3EU (020 7722 9301) Swiss Cottage tube until 8th May (£15-£25)