Like a rock star, Norman Rosenthal sweeps into his favourite Soho café (which does not open until half an hour after he commands me to be there, leaving me standing on a chilly street), one and a quarter hours late for our interview. And, like a rock groupie, I wait patiently, unwilling to relinquish my grasp on this big beast that I've been stalking for three months.

A dinosaur of a big beast in some ways; he blames his lateness on not understanding his iPhone, which has been on silent mode since last night and thus not relayed my increasingly anxious messages about whether I am being stood up.

I am not. But I suspect he regards me, an outsider rather than an intimate of the charmed inner circle of international art world luvvies in which he moves, as not quite worthy of an audience.

This is a man who, like many a rock star, feels free to let rip if he feels crossed - he famously spat at an art critic who dared to criticise one of his shows within his earshot on press day, and while working at the RA dismissed as not the equal of their peers the majority of living Royal Academicians whose artistic prowess the institution exists to honour.

Not that Rosenthal, with his dead-fish eyes and deadpan manner, is an actual rock star, in spite of the arrogance, untamed coiffure, flamboyant suits and regal attitude for which he is famous. Yet he is showbiz all the same; this entrepreneur's great talent is his panache in bringing art to the people and making it pay for the sponsors.

It’s great to just stumble across things, you can still dig up great stuff

The Royal Academy would likely be dead in the water without Rosenthal at its helm as exhibitions secretary for more than 30 years.

I first met this dynamo, who has no art or art history qualifications, just a great eye - including one for the zeitgeist - when he was getting ready to unleash Sensation, with all its bad-boy (and girl) Young British Artists, on the august and struggling institution.

The show outraged critics, visitors and Royal Academicians alike, but it packed the punters in, and the gallery has understood the value of blockbusters and followed Rosenthal's lead ever since.

But we are here to talk about life after the RA, which he left, gonged but unloved, in 2010 to pursue a future as a freelance curator. Speculation ensued about whether he had been pushed, but it was actually criticising the Academy for its lack of vision in a piece for The Spectator, which led to him getting offered the job in 1977.

He had held the same position of exhibitions secretary at the ICA - not bad for someone whose art career started with a holiday job in a Bond Street dealership.

"I actually wanted to sell records at HMV on Oxford Street, but they had no jobs so I went around the corner to Agnews," he explains, leading me around the corner himself to his warren of a Dickensian walk-up duplex, every inch of wall covered with a range of visual treasures spanning at least six centuries. "Just don't call me a collector," he snaps. "I just find things I love and buy them, like I just fell into the world of art."

Although his mother, who arrived as a refugee from Hungary one month before war broke out, played her part in stimulating his interest, he concedes: "Jews are very good, even when there's very little money around, in seeking out culture. My mother took me to the National Gallery, we went to Kenwood, and by the age of nine I was taking myself to the theatre to see Vivien Leigh and Laurence Olivier."

Born in 1944, Rosenthal got a state education at St Saviours primary school in Warwick Avenue - "at the time when the area was still slummy" - and Westminster City School, while his father, who arrived in the UK during the war with the Free Cezch Army, ran a restaurant for Czech refugees, "and was a bit of a gambler". But even before he had left university in Leicester, the young history undergraduate was organising his first art exhibition, Artists in Cornwall, for the Leicester Museum and Art Gallery. No wonder Agnews snapped him up on the spot for a holiday job that lasted three years.

Knighted in 2007, Rosenthal is universally acknowledged with having put London at the centre of the art world during his RA years, championing artists originally reviled by the establishment, from Damien Hirst to Tracey Emin to Sarah Lucas, from whom he has just commissioned a new sculpture for the smart new Nine Elms development abutting the new US Embassy site.

It's just one of the diverse consultations into which he has thrown himself between assembling shows everywhere from Berlin to Istanbul, sorting out a Warhol exhibition this winter for the Ashmolean and flying to and from Madrid, where his wife of 25 years, Manuela Mena Marques, mother of their two London-based daughters, is a curator at the Prado.

But now he is getting ready to step out in London again, making his next major appearance in the capital at the Frieze London Art Fair in Regent's Park this month with an audacious project.

He is curating eight little collections he believes would be worthy of space in the V&A, RA or other great public institutions - "showing that it is still possible, with knowledge and love, to put together outstanding collections of art that demonstrate the highest level of creativity in many different periods of history".

These will include categories of objects never seen at Frieze before, from unfashionable Italian maiolica - "When did you last see an exhibition of maiolica?" he barks - to Egyptian carvings to Paleolithic stones.

There will be German Expressionist portraits from the likes of Kirchner, Grosz and Beckmann based on the Renaissance tradition of "kopfe", or woodcut heads; and perhaps of special interest to Jewish visitors a selection of Japanese netsuke, the kimono ornaments so beloved to the artist and writer Edmund de Waal's Jewish family and eloquently described by him in his memoir The Hare With Amber Eyes. Crucially for Frieze, his co-curators are European gallerists who would not otherwise have a presence at the show (the netsuke are from the London dealer Sydney Moss).

Yet Collections is an oddly named project for a man who says he's opposed to the idea of setting out to make formal acquisitions and categorise them: "It's better to just stumble across things - and you can still dig up some great stuff in Portobello, if you know what you're looking for, like the Ruisdael print I picked up of a Dutch 17th-century Jewish cemetery. Two prints were made, and now I have the pair."

They are among a few items of Judaica he's surprisingly proud to own for a man who can't abide synagogues: "The last time I put my head in was Yom Kippur about 15 years ago," he says of the old Dean Street shul down the road from his flat. "I found it intellectually embarrassing." On the other hand, he says: "I would never deny my Jewishness."

He has, however, denied the right of Holocaust victims to restitution of their looted art at the expense of public institutions like the Belvedere in Vienna, which lost the stunning gilded Klimt portrait of Adele Bloch-Bauer that once sat beside The Kiss in a room that no longer knocks visitors' socks off.

Rosenthal outraged many Jews by writing in The Art Newspaper: "Grandchildren or distant relations of people who had works of art or property taken away by the Nazis do not now have an inalienable right to ownership…If valuable objects have ended up in the public sphere, even on accounts of the terrible facts of history, then that is the way it is."

But you need to read between the lines, because his real argument is that when looted art that, like the Klimt, is a representation of an era of Jewish history, the community is the loser if the art disappears back into the private sphere.

It is why he quickly adds a rider to the last outrageous thing he says to me about Israel being "Hitler's last revenge".

"By which I mean simply the grief the country has caused its own people as well as its neighbours with all the troubles and hostility. However, I can understand completely why Israel exists and that its setting up was completely inevitable."

Sir Norman Rosenthal is nothing if not an iconoclast.