Mark Fraser starts his new $500,000 a year job on Monday as director of a private museum that has yet to be built. But when it is completed, in another two years or so, the $50million-plus Museum of Old and New Art outside Hobart will house a vast collection of works ranging from antiquities to Australian and European paintings.

After 19 years with Sotheby’s Australia, the last four as the company’s managing director, Fraser has been hired by David Walsh, the multi-millionaire reclusive collector, investor and gambler who has commissioned architect Nonda Katsalidis to build his new three-level, cliff-face museum on his Moorilla Estate Winery.

Walsh was revealed as the mystery bidder at a Sotheby’s sale in April last year when he set an Australian auction record by paying $3.17million for John Brack’s iconic painting The Bar. It will join a growing number of major works in his museum which will be the biggest private gallery in Australia and will be open free to the public.

Fraser won’t comment on the financial details regarding his new position. But, as he is believed to have been on an annual package worth $300,000 at Sotheby’s, it’s safe to assume Walsh would have offered him a lot more.

The Cambridge-educated auctioneer first started bidding for pieces of decorative art when he was 14. He arrived in Australia in 1988 with a letter of introduction to Sotheby’s Patricia McDonald who was cataloguing an exhibition for the Bicentenary, but in June that year joined Sotheby’s and slowly worked his way up the hierarchy.

“I’ve done everything from shifting furniture around – and I’ve got the hernia scars to prove it – to learning about the full range of things we sell and being passionate about it,” Fraser once told me.

He says his association with Walsh started long before the Brack painting appeared in the Sotheby’s catalogue and that the collector has played a “very significant part” in the art market.

“He’s been collecting for years and is very passionate and excited by art in all its forms,” Fraser says. “He’s not a trophy hunter and when his collection goes on display it will be different: he wants to stir up debate, challenge people and have them discuss the collection rather than simply approving or disagreeing with what they see.”

Fraser dismisses newspaper reports that claimed the Walsh collection was worth $10million, saying no-one would build a $50million gallery to house a $10million collection when just one of the paintings alone cost nearly a third of that sum. In any case, he says the collection isn’t limited to Australian art works, although the bias is Australian.

The collection already includes indigenous art, antiquities, West African tribal art, ancient coinage and, of course, a considerable body of Australian paintings – many of which no doubt came through Sotheby’s. Fraser says his role will be to advise on the collection and yes, he will be back in the auction room bidding for new works both in Australia and overseas.