THE CONVERT is an important play. Two years ago, Danai Gurira’s debut Eclipsed, set in Liberia during the civil war, had its UK première at the tiny Gate Theatre, in Notting Hill, London. It went on to be nominated for a Tony award after a season on Broadway. There is every reason to think that her gripping new play might do the same.

It explores an aspect of Christian history which is rarely seen on stage. It is set in 1895 in Zimbabwe (then undergoing British colonisation, and shortly to be declared Southern Rhodesia in 1898); but the impact of the events the play portrays is still felt in the churches of every multi-ethnic city in England.

The mission house of Rosie Elnile’s set has aspirations to be genteel, but the furniture is faded, red African earth is breaking through its corners, and under the cushions the housekeeper (Clare Perkins) has placed fetishes from the tribal religion into which she was born. She converted pragmatically to Christianity when the Roman Catholic missionaries came, but African customs prove too deeply rooted to leave behind.

Now the missionaries have moved inland, leaving the house and the task of converting his countrymen to Chilford Ndlovu (Stefan Adegbola), who has adopted the tailcoat, language, and manners of European culture.

Into that setting comes Jekesai (Mimi Ndiweni), who will convert to anything that allows her to escape arranged marriage to a brute. Chilford renames her Ester. She is a quick learner and a deep thinker. Her journey into Christian faith is genuine, and she becomes the mission’s most effective evangelist. She loves the family she has left, especially her cousin Tamra (Michael Ajao). But to them the converts are bafu, black men and women who have acquiesced to the ways of the white colonisers. This puts her in a dilemma that will eventually cause violence to erupt into the house.

The fascination of Gurira’s play is that Christianity is a liberating blessing, but conversion does not bring instant transformation. The culture it liberates people into also opens the possibility of materialism, whisky, and racism.

Christopher Haydon’s fine, even-handed production is too tense for laughs. There is, however, a joyful use of language. The Africans who are eager to adopt the English of the Church over-translate (“Please, be absolving me”). But those who have not really forsaken tribal religions just get in a muddle (“Hail Mary, full of ghosts”).

The performances are impeccable, notably from Mimi Ndiweni, as she transforms from naïve and scared Jekesai into confident but compromised Ester. In the final moments of the play, which anticipate the new churches that would grow in Africa under indigenous leadership, she is radiant. She will send any clergy in the audience out into the London streets deep in thought about whether the fast-growing Black and multicultural Churches can engage appropriately in cross-cultural evangelism in a land that once sent missionaries throughout the world.

The Convert runs at the Gate Theatre, 11 Pembridge Road, London W11, until 11 February. Tickets: www.gatetheatre.co.uk or phone 020 7229 0706.