“Everybody’s got the right to their dreams” is how we are introduced to nine assassins - or would-be assassins - of American presidents, from Abe Lincoln all the way up to Ronald Reagan.

This seems a somewhat clumsy sentiment in the hands of such a master of the musical theatre as Stephen Sondheim, who wrote the music and lyrics of this 1990 show (book by John Weidman); but this is a more than usually challenging subject, even for him.

The main problem is that by choosing as your characters nine people from different periods in history, only two of whom appear to have actually known each other, you are setting yourself a huge challenge in making them interact in any meaningful sense. That Sondheim succeeds as well as he does is a sign of his particular genius, but it makes for a show that strains somewhat desperately for a narrative drive.

It also makes for a show that is a little hard on its audience, with an interval-free performance of two hours’ duration. That gripe aside, there is a great deal to relish in this production by Michael Strassen. For starters, it's superbly orchestrated (by Richard Bates) and wonderfully sung.

The main conceit is that the assassins form an immortal confederacy who urge others to emulate them in order to keep their deeds, and their names, alive. Thus John Wilkes Booth emerges from the shadows of the Texas Book Depository to persuade Lee Harvey Oswald not to kill himself, as he had intended, but to turn a rifle on JFK instead.

The tone is arch, wry and detached – and Sondheim has to work very hard to inject passion into the proceedings, and to give us a little humanity to hang on to. The result is some hugely enjoyable performances, but a piece of theatre that can never really get under the skin of so many disparate malcontents.

In particular, Nick Holder impresses as a sweaty Samuel Byck, who wants to fly a plane into Nixon’s White House; so too does John Barr’s clownish Guiteau, who assassinated President Garfield for thwarting his ambition to be US Ambassador to France. Glyn Kerslake is self-righteous, smooth and magisterial as Booth, and Nolan Frederick’s Balladeer links the stories together with panache.

This may not be Sondheim at the peak of his form, but it is dark, funny, ambitious, and another triumph of musical staging at this address.

- Giles Cole