Defy the traffic beside the Houses of Parliament and you can see, to one side, Henry Moore's Knife Edge Two Piece and to the other, Rodin's The Burghers of Calais. Or you could do, until what the French sculptor called "my novel" was trundled up the A10 to Perry Green in Hertfordshire, to Moore's home, studio and gardens. Here, for the first time, the great modernist's work is being shown alongside that of another artist. Other collaborations will follow, but Rodin is the obvious first guest – Moore treasured an early volume about him, bought his work, liked the things he liked.
If you want to come face to face with the French martyrs before the autumn, then, head for Moore Rodin. And face to face it is – the brave citizens who were designed to stand four-square on the ground, were, once installed at Westminster in 1913, so dwarfed by their Victorian Gothic backdrop, that Rodin sanctioned a plinth, so changing the vulnerable huddle of determined heroes to a lofty collection of municipal worthies. Planted at Perry Green at their intended level, between the shrubs and trees, they shrink rather than swell with proximity, a trick of scale that runs through a show in which the colossal is often delicate and the miniature impregnable.
The nude figure of Calais martyr Jean d'Aire, straining fists clenched to surrender the keys to his town, is a prototype for the Burghers. Each was modelled naked then "dressed" in plaster-soaked folds so that the immense strength of resolve is not a final flourish, but comes from within. Every dimple is cavernous, every sinew stretched.
Most of the consoling monoliths and groups of Moore are in their usual home, but now, through their scoops and curves we can glimpse their Rodin counterparts, as handpicked by curator Anita Feldman, largely from the Musée Rodin gallery and garden in Paris. While lambs gambol prettily in the iced meadow, the Yorkshireman's vast and tender figures settle benignly into the landscape – here, Three Piece Sculpture: Vertebrae (1969), with its dinosaur joints, there, elephantine Arch (1969).
Smaller works, in the gallery, show synergies of material and subject: mother-and-child embraces, women intimately observed, figures that appear to emerge fully formed from rock or recede into it. There are moments when the labels could be swapped without anyone suspecting.
Both sculptors delighted in tiny miracles of nature – intricate seashells, teasing stones. Both elevated special finds from the natural world on little plinths. Both toyed surreally with their own maquettes, planting them in antique vessels. Both modelled and drew unceasingly, Rodin stockpiling limbs and torsos, Moore fashioning figures in the image of the quirky flints and bleached bones he squirrelled into the studio that brims with found objects and the maquettes they inspired.
You long for them to have met. But Rodin died in 1917 when Moore, at 19, was in the trenches. Their meeting of minds is suggested in a combined collection of favourite possessions: Rodin's Ancient Egyptian ibis, Moore's Hittite ox; Rodin's Hellenistic female figure; Moore's 14th-century tomb angel; Rodin's skipping Aphrodite; Moore's early 20th-century dancer, work of one Auguste Rodin.
We run the risk of glancing nonchalantly at the work of much-loved artists such as these, favoured by public collections and spaces. The London borough of Tower Hamlets, in trying to flog off its superb Moore, Draped Seated Woman, has a bad solution for such bronze fatigue. Instead, this show refreshes tired eyes, and unveils the unfamiliar.
Tucked away in one case, only a few centimetres high, is Moore's coloured-concrete Torso (1926). As unexpectedly taut and tense as a Rodin and uncharacteristically futuristic, it was acquired by Perry Green last year, and has not been seen by the public since the Twenties. That alone – and everything else – makes the show unmissable.
The Henry Moore Foundation (01279 843333) to 27 Oct; Compton Verney, Warwickshire (01926 645500), 15 Feb - 31 Aug 2014