It’s a superbly evocative word — maharaja. Yet beyond the rough and obvious truth that it describes an extremely rich Indian prince with a taste for rubies and dancing girls, I find myself googlied by its fuller meaning. What do I really know about the maharajas? Not much. At least, that was the regrettable state of affairs before I toured the V&A’s astonishingly expensive-looking investigation of this mysterious breed, where all was revealed. Now I know that the maharajas were actually far, far richer than I had originally assumed. And that they adored their rubies much more fiercely than I could ever have imagined. As for the dancing girls, Ram Singh II of Kota even had one perform for him as he rode his elephant, on a platform built out onto the beast’s tusks.

So you have to hand it to the maharajas. We’ve underestimated them. Their talent for exploiting their populace and growing rich, disgracefully, was close to super­human. That admitted, I see the V&A has set out to understand them in deeper and different ways.

Every now and then in this display, you encounter a map of India placing a particular nawab, nizam, rana, raja or sultan — the maharajas were a federation of royals, rather than a single species — in his shifting geographic kingdom. There are newsreels, too, and documentary-style black-and-white photographs of jewel-encrusted maharaos with curly moustaches meeting stiff British dignitaries with brooms up their jackets. On one of its strata, the show harbours an ambition to locate the maharajas in the full history of their times. But trying to hear this documentary message above the roar of the surrounding diamonds is like listening to a chirping robin while standing next to Niagara Falls. Yes, the maharajas may have played an interesting role in the jittery relationship between India and Britain. But what really matters here is the size of their rocks.

I have seen goose eggs smaller than the yellow diamond at the centre of the great necklace commissioned from Cartier in the 1920s by Maharaja Bhupinder Singh of Patiala. It was the largest single commission ever received by the finest French jeweller. And what of the string of huge emeralds worn by Ranjit Singh’s horse in the 1830s? Wouldn’t the weight of all that priceless stonewear around its neck have slowed the nag to a hobble? At one point in the glitterfest, I found myself staring at a slab of blue glass, roughly the size of a pear, set into the centre of a turban monument from Murshidabad. It turned out to be several hundred carats of uncut sapphire.

So, yes, the maharajas may well have formed a crucial symbolic layer between heaven and earth, as the V&A claims. And yes, they may well have played a semi-divine role in the post-Mughal restructuring of Indian society. What really counts here, though — the brutal truth about them — is that few creatures in history have lived as splendidly or greedily or ridiculously as this.

The show has a spectacular opening, with a full-size model of a marching elephant hung densely with extra-large maharajaish ornament. The news that the maharajas were partial to ostentatious parades is hardly surprising. Every despot who has ever lived, from Julius Caesar to Mao Tsetung, has chosen to communicate with his people via the showy Esperanto of the big parade. The V&A, however, is keen to remain culturally diplomatic, so it appends some hopeful explanations to its treasures of the ancient Sanskrit concept of maharajadhiraj, meaning “king of kings”, as well as a few elegant ruminations on the complex process of Indian states­craft. It may all be true. But it’s not nearly as true as the more obvious fact that here was a race of power-hungry absolute rulers who emerged in India in time to fill a beckoning political vacuum, and whose appetite for wealth and kudos drove them to extremes of ostentation the world has rarely seen.

Interestingly, all these maharajas who carved up India after the terminal crumbling of the Mughal empire in 1739 could be Hindu or Muslim. Their most important qualification was their ability to fill a power vacuum, not their religion.

The middle portion of the show is spent trying hopelessly to understand the complex triangulation of power between the maharajas, the East India Company and Britain that eventually gave rise to modern India. Fat chance. If the most remarkable thing about the maharajas was how ostentatious they were, their next most remarkable quality was their ruthless self-interest. With rare exceptions — such as the spectacularly angry Tipu Sultan of Mysore, who swore never to cease fighting the invader — the playboys and polo-players-in-waiting who make up this mightily mustachioed cast appear shockingly content to let the British rule India.

Some of the most spectacular loans in the show come from our own Royal Collection, where they arrived as oily diplomatic sweeteners. The Koh-i-Noor is absent, but the solid gold tea service presented to Victoria by the Maharaja of Mysore is here. In return for these huge piles of rubies and diamonds, we, hilariously, gave the maharajas dictionaries and commemorative plates. Thus, the real journey we follow here is not the glorious tale of the maharajadhiraj, but the much more recognisably human collapse of a ruling class neutered by political cowardice and snobbery. In the end, the lot of them were rendered obscenely useless by that debilitating fondness of theirs for luxury.

Some of the most elegant objects turn up in the final room, where the top brandmakers of Europe are kept busy supplying the maharajas with their gewgaws: Cartier diamonds; handmade Louis Vuitton luggage; the most beautiful custom-made Rolls-Royce I have ever seen. The kings of kings have completed their tragic meta­morphosis into a race of Harrods shoppers.

Maharaja: The Splendour of India’s Royal Courts is at the V&A, SW7, until Jan 17, 2010

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