The last time I visited the extraordinary rock garden at Chatsworth House, back in -ouch – 2014, my overwhelming impression was ‘yellow’. It was majestic, of course – the sheer amount of – well – rock – is a jaw-dropper, but I couldn’t have named a plant or noted a specific area that came to mind. A vague memory of general ‘yellow plants’ pervades my memory.

On Friday I finally got to see Tom Stuart Smith’s revolutionary re-imagining of the space and, three days later, I am still bowled over. It helped, of course, that making a beeline for it as soon as I arrived meant there was still some of that magical Derbyshire mist floating over the water, creating a mysterious arcadia that could not be anywhere else but England.

The rock garden was begun by the 6th Duke of Devonshire in 1842, as a souvenir of the Alpine splendour he’d encountered on the Grand Tour but in many ways the garden is also a love letter to its surroundings: Chatsworth’s very own peak within the Peaks. It is modelled on a chasm at the family estate in Yorkshire, yet everything screams ‘Derbyshire’. Even the stone was brought from a local quarry at Dobb Edge, ensuring the boulders look entirely natural.

I have no proof (yet) that Ellen Willmott ever visited Chatsworth but I can’t help feeling that this ‘chasm’ – in turn based on one at Bolton Abbey in Yorkshire – at least part-inspired her own ravine at Warley.

And yes, of course she was inspired by her many trips to the Alps, but Warley’s gorge also owes a great debt to the English countryside and, I can’t help feeling, to the grandeur at Chatsworth. I fully expect to find photographs of the estate at some point of our excavations.

Ellen had Yorkshire firm Backhouse & Sons transport many tonnes of Derbyshire stone to Essex, which may account for the similarity of the rocks to those at Chatsworth.

Naturally, Ellen’s planting used a lot of alpines – she even poached Swiss alpine gardener Jacob Maurer from her mentor, Henry Correvon, to tend her vast collection of rarities. From her own photos, and from irritated letters from Correvon, however, we also know that she just couldn’t resist using a wide range of plants, including the hardy perennials that most people were using in their herbaceous borders at the time.

Correvon tells her off for using cotoneasters as having no place in the rock garden. Ditto double flowers and, worst of all, mahonia. Ellen’s own photographs reveal a delightful jumble of grasses, conifers, ferns, bulbs, shrubs, and general herbaceous perennials, none of which should have had ‘a place’ in alpine gardens. Hell – she even used bamboo among the stage-bright mounds of tiny alpine jewels. Yet, people flocked from miles around to see this inspired collation that paid no heed to convention.

Nineteenth century rock gardens have had a tough time over the last century or so. Wildly popular when there was enough labour to tend the fussy little alpine plants that generally populated them, their appeal took a dive after the First World War when young men were at a premium, and they’ve suffered ever since. Famously, Ellen’s garden became a ruin. The boulders of her famous alpine ravine are now up to their necks in leaf mould.

Yet Chatsworth’s majestic peaks have remained and have always been worth a visit.

I was not prepared, however, for the soft grandeur of Tom Stuart Smith’s reimagination of these richly-weathered boulders. Not prepared for the undulating paths, the craggy entrances and exits, the power of sheer rock face with its crashing waterfalls. Not prepared for the aching delight of a deceptively simple planting that sings directly to the heart.

By rolling with the times, mixing high and low, embracing the lush glow of perennials over the fussy glamour of pure alpine plantings, under Tom Stuart Smith’s expert eye, Chatsworth manages to be both exuberant and intimate. The visitor finds themselves easing their way through a ‘mountain pass’ of tight rocks then walking an expanse of path that allows them to concentrate on the view instead of their step.

Pinks and purples, whites and a tapestry of greens and silvers are punctuated with the dark red of martagon lilies, their centres echoing the homely, earthy glow of moss-covered rock.

The visitor is encouraged to wander, high and low, to linger by still pools, cloaked with gunnera and ferns, to perch themselves on seats soaring above even Wellington’s rock, to soak in the cool plantings part-hidden by the mists below.

Even the ‘rough’ grass between the tumbling waves or peonies, campanulas, irises and the odd, perfectly-placed acer, speaks of a timeless, natural world in which nothing is out of place if it is beautiful.

I have the feeling that Ellen Willmott may even have enjoyed this incarnation of Chatsworth’s corner of the Alps more than the one I am sure she encountered back in the day. It certainly echoes her maverick attitudes to alpine gardening. For me, three days after encountering it myself, that valley still haunts my imagination. I think I can truly say that this 21st century reimagination is now one of my favourite gardens, full-stop.