In this musical adaptation of one of Graham Greene's later novels, we enter a very strange world. Greene's naturally louche milieu - the mythical ‘Greeneland' - takes on a more comic appearance as mild-mannered bank manager Henry Pulling finds his world turned upside down by the appearance of his aunt. Ron Cowen and Daniel Lipman's book is closer to the plot of the George Cukor film than to Greene's original novel but it features twists all of its own.

Patricia Hodge captures well the full force of the formidable aunt Augusta: her thirst for adventure, her taste for luxury and can-do attitude overwhelms Henry. It's a meaty part and Hodge tackles it with lip-smacking relish. The only sour note – and it's an important one in a musical – is that she's not got a strong singing voice.

Nor for that matter has Steven Pacey, who plays the put-upon Henry, although it is better than Hodge's. However, he does excellently in conveying both the strait-laced demeanour of a middle-aged, middle-class Englishman while showing flashes of steel beneath.

Much of the life in the production is provided by Hugh Maynard's Wordsworth, Augusta's lover and devoted ally. It is he who gives much of the musical spark.

George Stiles and Anthony Drewe's songs are pleasant enough, veering from the calypso-like "Keep Moving" to the plaintive "A Feeling I Call Home" but there are no actual show-stopping moments and no tunes that had the audience singing on the way out.

Perhaps the strangest thing about the production is the setting. The action supposedly takes place in 1969 but the whole atmosphere is something more akin to pre-war Europe. There are references to cannabis and some flashes of psychedelia in some of the costumes but they seem almost afterthoughts. Haley Flaherty's wide-eyed hippy Tooley seems to have wandered in from another play entirely. Certainly Colin Falconer's excellent set, based on the railway stations of the aunt's wanderings, would do excellent service in a 1930s spy setting.

Overall it's a pleasant evening, but I left feeling that, such was the richness of Greene's original material, this could have been so much more than pleasant.

Travels With My Aunt runs at Chichester Festival Theatre until 4 June.