Idris Elba's Tree: Will Gompertz reviews the star's new work in Manchester ★★★☆☆

If you are an à la mode celebrity working in the creative industries it is entirely possible you will receive a tantalising note from the Manchester International Festival (MIF) asking, "is there something unique you'd like to do that we can help make happen?"

It is a licence-to-roam invitation that proved irresistible in previous editions to Marina Abramović (The Life and Death of Marina Abramović ), Damon Albarn (Monkey: Journey to the West), and Björk (Biophilia). Their shows were typical of the biennial festival, tending towards the experimental and experiential.

Björk performing at the Manchester International Festival in 2015

This year the actor Idris Elba took the bait.

He'd been thinking of turning his 2014 album mi Mandela into a theatrical piece; the MIF 2019 solicitation was the tipping point: a play called Tree is the outcome (acted by others, not Elba).

It tells the story of Kaelo, a mixed-raced London lad (Alfred Enoch) who goes to South Africa to scatter his mother's ashes. He stays with his tough-as-teak Afrikaner granny (Sinéad Cusack) who faces losing her farm through new land reform laws. He is clueless; she knows more than she's letting on.

And so we have a young man seen as a black Englishman and an old white African woman at the heart of a play that engages with the complex subjects of race, belonging, family and change with conspicuous intelligence and originality.

Sinéad Cusack stars as wealthy and resentful South African, Elzebe, with Alfred Enoch, who plays her grandson Kaelo

Kwame Kwei-Armah's lively direction adds spectacle and grace.

Tree is precisely the sort of show for which MIF was created. It is a play given the freedom to be different; to challenge convention.

The informal vibe in Manchester's Upper Campfield Market Hall where it is presented before a run at the Young Vic in London at the end of the month, felt more like a gig rather than a traditional hush-hush, straight-laced, po-faced proscenium arch affair.

You are invited to dance on stage before and after the show, while during it the actors walk through the audience who are standing throughout (you can sit, but all you'll see is the back of people's legs).

It is a spirited, spiritual production.

Idris Elba and Kwame Kwei-Armah say they wanted to create a piece of physical theatre that included the audience in the storytelling

There is one major problem, though.

The writing is not very good. At best it is prosaic, at worse, plain bad.

There is not a memorable phrase in the piece, the jokes are corny, and too many of the script lines leave a very able acting ensemble looking wooden and awkward.

Tellingly perhaps, there isn't a writer listed in the credits. Idris Elba and Kwame Kwei-Armah are named as the show's creators - a claim contested by Tori Allen-Martin and Sarah Henley who say many of the ideas in it are theirs (ironically, disputes over ownership of property rights are a central narrative element of the play).

Idris Elba says the songs in his album mi Mandela represent a personal journey inspired by his role as Nelson Mandela in Long Walk to Freedom

Idris Elba with director Kwame Kwei-Armah, who was inspired by mi Mandela to "create a story about the ambition to heal"

Maybe transforming an album into a dramatic event with atmosphere and movement was the creative focus. It does that well.

But the story is told with words and they do not appear to have been given the same level of love and attention. The net effect is the intricate, nuanced plot that structures the piece is reduced to an occasionally bland 95-minute fable told by characters about whom we are not always made to care enough.

A play without a playwright is like a garden without flowers: a pleasant enough escape, but bereft of beauty and character.

In most cases, that would be that.

But this is MIF, and MIF is different.

It is not a festival seeking perfection, its aim is to encourage risk-taking; to push those with whom it collaborates to go beyond their comfort zone and attempt something fresh.

It is a festival for the creatively courageous.

Tree is a fine example of that spirit of adventure.

A tense moment between Elzebe (Sinéad Cusack) and Ofentse (Joan Iyiola), who plays Kaelo's half-sister

It is not perfect, few shows at MIF are when they premiere - most have a rawness to them.

But it is well worth seeing. Particularly if you like your theatre loud, fearless, and funky and don't mind a few rough edges.

Recent reviews by Will Gompertz

• George Clooney's Catch-22 ★★★☆☆

• Paula Rego show in Milton Keynes ★★★★★

• Cindy Sherman at National Portrait Gallery ★★★★☆