The best fun on the Fringe

This pulsating cabaret-style musical by Dublin's Rough Magic company is an absolute gem. Set in wartime neutral Ireland, it's a surreal satire about national loyalties and Anglo-Irish relations, of the political and intimate kind. And quantum mechanics.

It's 1941 in the Free State capital, where British Intelligence has sent posh, prim but naive codebreaker Tristram Faraday (beautifully played by Peter Hanly) to investigate rum goings-on in a nationalist bar not far from a radio station where suspicious musical requests are being played. Could the Irish be collaborating with Nazi Germany by sending coded messages in song titles about shipping movements? And is the comely colleen Philomena (another star turn by Lisa Lambe) one of us, or one of them?

In a story brimming with mad ideas and ridiculous coincidences but with little regard for historical fact, Faraday rubs shoulders - and swaps witty barbs - with Erwin Shrodinger (of Cat fame), writer Myles Na gCopaleen and poet John Betjeman, here an MI5 colleague.

Writer and lyricist Arthur Riordan provides an indecently funny script - think PG Wodehouse meets Tom Stoppard - and composer Bell Helicopter's score matches it for wit and invention; it's played by four onstage musicians, led by Cathal Synnott. My favourite songs were the alphabetical essay on sex A, E, I, O, U! (say it out loud and you'll get the joke) and the wonderfully racist Eire for the Eireyans.

Lynne Featherstone directs the multi-talented cast of six with a sure hand, melding song and dance seamlessly with absurdist theatre in a production that fizzes with energy. My one cavil is the unnecessary interval, which annoyingly interrupts proceedings that otherwise gallop along in a theatrical tour de force. But no matter - this is the most fun you'll find on the Fringe.

Improbable Frequency
Traverse, Edinburgh