Here's a delightful how-de-do. The tiny Union is onto its fourth musical - and second all-male production of Gilbert and Sullivan - in a year and it's simply getting better and better.

The noise the chorus makes is the loveliest I've heard for months and would be the envy of most West End shows. This production team is going places.

The first place it's off to is the wonderfully topsy-turvy realm of Titipu, a world of mock-Japanese silliness, where demotions, revelations and executions tumble gaily through the plot.

The musical numbers could easily be mistaken for the running order on a G and S Greatest Hits album, and the 13-strong cast attack them with relish.

In every respect musical director Christopher Peake is a one-man band, but what he lacks in colleagues he more than makes up for in commitment, providing assured piano accompaniment for every song.

The three little maids have marvellous falsettos - and, in Vanessa Fenton's subtle choreography, nifty parasoltwirling skills - with a fluttering Martin Milnes giving the turn of the evening as Yum-Yum.

Director Thom Southerland could add a little more pep to some sections of dialogue, especially when they're establishing for us "Titipudlian" arcana. But anyone who gets group numbers sounding and looking like this is doing a whole lot right.

Surely such a treat shouldn't just be confined to Southwark?

Until 16 August (020 7261 9876, www.uniontheatre.org).