Miss Saigon – one of the great musicals – opens with the thundering rotor blades of a helicopter, the sound seems to rumble overhead so realistically you find yourself looking upward in the theatre. This is Puccini’s tearstained Madam Butterfly transposed to Vietnam in the closing years of that most shameful war.

Ken Burns and Lynn Novick’s epic 2017 TV documentary The Vietnam War (10-parts, 17-hours long) laid bare the war – from political fumbling in the Nixon administration to barbarous acts in the field. The American GIs R and R in Saigon gave layover a new meaning. Drugs and prostitutes helped the soldiers’ traumatic stress if only temporarily.

At the Dreamland go-go bar (with its wonky neon sign) Sergeant Chris (Ashley Gilmour) falls for new face Kim (Sooha Kim) who has newly arrived from the country and as a virgin has a special appeal for the joint’s sleazy owner and pimp-in-chief, the Engineer (Red Concepción). Chris and Kim spend the night together and find true love while Saigon falls around them. But her father has promised her to Vietnamese boy in an arranged marriage. It’s “a world where nothing can last”. But maybe, just maybe, their love can.

The story recalls South Pacific and Cinderella but what producer Cameron Mackintosh, Alain Boublil (book and lyrics) and Claude-Michel Schoenberg (concept, book and music) pull off in this Tony-laden, emotionally-charged tour de force is something really very special. (Mackintosh has made some judicious tweaks for this current outing and it’s better than ever.) The operatic score and heart-rending story are abetted by fantastic moving sets that conjure up dirty streets, the jungle, the American embassy gates where hapless Vietnamese clamour for visas and the promise to be airlifted to safety.

The show is mounted with imaginative brio – there’s an exhilarating sequence with flags and drums and a giant golden bust of Ho Chi Minh. And when Kim and her Bui Doi (a child born to one of the GIs who is neither Vietnamese nor American and seemingly unloved and unwanted by either) seem to be lost in the ruins you pray that all will all come right in the end. She sings that she will give her life for the boy or take the life of anyone who threatens him. And you believe her.

There’s not an ounce of slack in the direction (Jean-Pierre Van Der Spuy). It’s a thrilling, gut-wrenching night of theatre with some fantastic performances (a special shout-out to Na-Young Jeon who plays Gigi, one of the go-go girls).

Prepare to be emotionally drained.