A gantry, a couple of ropes and a big step-ladder are all that Thom Southerland’s production needs to suggest a ship. To evoke size, the excellent cast — who brilliantly double-up as upper class and below-stairs passengers and crew — do something that reminded me of how people respond to the Grand Canyon. They stand dumbstruck, wide-eyed and open-mouthed at the sheer scale of the thing. To this, add spine-tingling singing, often climaxing in appropriately stirring choral crescendos.

Maury Yeston’s 1997 multi Tony-winning musical, which opened six months before James Cameron’s movie, is an education. Maury’s lyrics and Peter Stone’s book are full of fascinating facts — how much steel was used, how many oranges were on board and, still shockingly, that there were 450 empty places on the lifeboats when the ship went down, killing over 1,500.

Even more illuminating, the show reveals that the captain was put under pressure by the ship’s owner to go faster than both he and the designer thought prudent. It’s all thrillingly staged and performed. But it’s not just the ship that sinks after it collides with the iceberg. So does the considerable tension generated before the fateful moment. Thereafter the show loses energy and momentum. It’s the fault of Stone’s book.

A more imaginative, less linear storyline could have positioned the terrible, climactic moment much nearer to the end of the evening.

Puns are all too easy with this superbly performed and ambitious show. But something is not quite right if you want to jump ship before the end of the final act.