What an odious toad of Toad Hall this is! In a new musical, with a book by Julian Fellowes, we get a thoroughly unrepentant, thoughtless, entitled toff, like Jeremy Clarkson crossed with a harrumphing landowner from, well, Downton Abbey. Rufus Hound delivers the part with the suitably inflated bumptiousness, but unlike the eventually conciliatory amphibian of Kenneth Grahame's original, this Toad proudly learns precisely nothing. It's a curious alteration – you'd more usually expect a musical to tack on a moral message, really – but without any kind of character arc the ending feels bumpy.

And frankly, I found myself hoping the weasels that squatted Toad Hall – shouting "property is theft!" – might prevail.

Putting, ahem, the weasely class politics of it all aside, this lavish family show manages to be both anodyne and rather jolly. There's a sprigged charm in George Stiles and Anthony Drewe's plinking score, parping and trilling and warbling about springtime and swallows. In a large cast, most animal groups get their moment, whether it's adorable wassailing field mice, comedy hedgehogs or slinky, smoky stoats in the wild woods.The chorus is sparkling throughout under Rachel Kavanaugh's sure direction, with Aletta Collins' choreography capturing some animal essence in angular leaps or sweet scurryings.

There's a nice central relationship between Mole – a winningly nerdy Craig Mather – and Ratty, who's played with alternately daft and deadpan wit by Simon Lipkin, far and away the best thing in the show (and the only really funny one). Their instant intimate friendship also feels moonily romantic, as they croon about how much they love "messing about on a boat with you". I wish they'd been allowed a quick smooch at the end when this song gets reprise.

A little peril – in the form of a baby otter being captured by those bad communist weasels – is inserted to up the ante, but otherwise it evokes the pace of Grahame's gentle, beloved children's tale. Still, Fellowes' book feels like it too often misses a narrative beat, or forgets to include character basics (why does Mole think only Badger can help Toad? What is Toad so famous for that he gets asked for an autograph?)

Peter McKintosh's design somehow manages to be both tasteful and toothsomely garish. Concentric circles of pale wood frame the stage, delicate willows sway above, and the animals' underground burrows are snug and cosily decorated as Hobbit holes. Toad Hall meanwhile is a headache of acid green, and there's a sugary but effective colour-coding or theming to the costumes of each tribe of critter; rabbits are camp footmen in emerald, weasels are spivs in plum pinstripes. Not sure about putting foxes in fox hunting outfits – bit cruel – but I did enjoy the water rat's stripy Breton top, and tail.

The colourful animal cutesiness may win over kids, but this Wind in the Willows ultimately feels overly glossy, obviously more West End than woodland and waterway. It's tweeness is too tame, lacking bite.

The Wind in the Willows is at the London Palladium till 9 September.