Siroe, Re di Persia begins with the curtain rising in silence. Jean Brodie is sitting on the stairs of a house whose wood panelling and wallpaper have seen better days. As she walks through the house, the stage revolves, revealing other rooms. She is carrying a cup and saucer and, when she comes to a mirror, she does a wee dance to her reflection.

Back in the hall, people in evening dress are clearly in a strop. Cosroe comes down the stair, and announces he is giving the crown not to his eldest son Siroe but to the younger Medarse. It is never quite clear why, unless it is blond, floppy-haired Siroe's resemblance to 1980s popstar Limahl. Only a fond father could be blind to the fact that Medarse (Antonio Giovannini) is clearly disturbed.

Meanwhile, Emira is masquerading in the house as a young man, Idaspe, while she waits her chance to avenge Cosroe's killing of her father. Anna Dennis is very convincing in her DJ and later a grey suit and cravat and she has an exquisite, pure voice. There is a magic moment later, when her voice and David Tayler's theorbo sound as one for a few bars of recitative.

Then there is Cosroe's mistress, Laodice, played by Aleksandra Zamojska as the sort of woman who gets blondes a bad name. Her every appearance is in a different outfit. She fancies her chances with Siroe, who isn't interested - secretly, he and Emira are in love; therefore, he must be destroyed. What she wasn't planning was Medarse chancing his luck with her.

Siroe (Yosemeh Adjei) ends up condemned because Emira/Idaspe's plot to kill Cosroe gets rumbled, and Medarse gets the credit. All the tension is, by this time, getting to Jean Brodie -the maid, played by Bettina Fritsche - whose nerves are frayed to the point of collapse by the time the curtain falls at the end of the first half.

Adjei is a hunk, with formidable musculature - we see him in boxing shorts at one point - which is just as well. He is shackled to a radiator in the cubby-hole under the stairs but is able to pull it off the wall and, eventually, to work himself free of the shackles. And he manages to sing gorgeously while in the most uncomfortable positions.

Meanwhile, Medarse is keen to accelerate his father's death and, thus, his accession to the throne. Cosroe (Lisandro Abadie) has aged more at every appearance, not helped by Medarse chucking his pills in the fireplace. Jean Brodie continues her work around the house, at one point bringing in a vase of chrysanthemums - such serviceable flowers.

When Cosroe learns the truth - including Idaspe's real identity - Medarse really loses it, douses the house in petrol and strikes extra long matches. The long-suffering Arasse (Ross Ramgobin), Cosroe's aide-de-camp and Laodice's brother, disarms him. Emira appears as herself, Jean Brodie wheels in a trolley of tea and cake - which Emira and Siroe jointly cut - and Medarse tries to get his hands on the crown. As the family finally sings a jolly chorus, the stage swings round to leave Jean Brodie enjoying a nice cup of tea.

Special praise for Okarina Peter's amazing costumes -Laodice's shell-pink gown emblazoned with a red scorpion - and Timo Dentler's shabby genteel set. Director Immo Karaman has created a household which needs to spend more time apart, and Laurence Cummings conducts the excellent FestspielOrchesterGöttingen as well as the exceptional singing.

It's enormous fun, but I can see why the purists might not like it.