Fred Williams' Hillside I sold for Aus$1.05m (£719,180) at Mossgreen's sale of the Dr Ann Lewis collection on November 7.

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The auction of Lewis's private collection attracted a 1500-strong crowd, where just about everything sold above estimate, bringing a total of Aus$3.4m (£2.33m).

The sale size, site and spectators reflect the collector's significance in the Australian art world. Lewis was director of Gallery A in Sydney from 1964 and championed indigenous and Australian art, both locally and internationally, for most of her life. She was a founding member of the Australia Council Visual Arts Board and served on the International Council of the Museum of Modern Art in New York.

The sale was viewed in situ, Dr Lewis's residence Amaroo in Rose Bay on Sydney's harbourside, where contemporary, idiosyncratic, younger artists sat comfortably alongside more established Australian artists' major works. Ron Ramsey, director of the Newcastle Art Gallery had likened the residence to "boarding an ancient ship laden with treasure".

The top lot of the night was a picture by one of Australia's greatest landscape painters, Fred Williams (1927-1982). Bidding on the large oil-on-canvas, Hillside 1, opened at Aus$900,000 and sold within estimate for Aus$1.05m (£719,180) to a telephone bidder who beat two other contenders. The picture was a tenth wedding anniversary gift from Dr Lewis' late husband and construction magnate John D. Lewis, and had hung in their bedroom. Maximum exposure was ensured before the sale, however, by putting the painting on public view at the National Gallery of Australia in Canberra for the past three months as part of the artist's first major retrospective exhibition.

Hillside 1 was painted in 1965 when, having returned from travels in Europe, Williams settled in Upway in the Dandenong Ranges just outside Melbourne. The steep bush-covered hills gave rise to a series of monumental landscape paintings. The highest price for a Williams is the Aus$1.6m paid in 2006 for a work from the same series when Christie's were still operating in Melbourne.

During her time at Gallery A, Lewis was responsible for seminal exhibitions, wild parties and launching the careers of some of the Australian market's best-known artists. It was the first gallery in Sydney devoted to abstract art and one of the first spaces in the country to exhibit Aboriginal artworks. The Mossgreen offering tracked the development of contemporary Australian art from the 1960s.

Three paintings by indigenous artist Sally Gabori (b.1934) sold for more than three times their upper estimates, setting a new artist's record of Aus$30,000 (£20,550) and proving that provenance is a key component for collectors of contemporary Aboriginal art. The previous record for a Gabori work at auction was Aus$6500 for an earlier Dibirdibi Country painting sold by Deutscher and Hackett, Melbourne in 2009. Lewis's bold 6ft 6in x 3ft 4in (1.98 x 1.01m) linen abstracts hung in her living room that overlooked a private beach and jetty.

Gabori only began painting at the age of 80 when she wandered into the Mornington Island arts and crafts centre in Queensland and picked up a brush out of curiosity. She had probably never been to an art gallery or seen the work of abstract painters from around the world but innately knew how to put colours together.

Gallery A hosted Rosalie Gascoigne's (1917-1999) first exhibition, after which she became the first female artist to represent Australia at the Venice Biennale. Her Summer Swarm, 1995 was another highlight, selling for Aus$220,000 (£150,100), well above the Aus$150,000 upper estimate. The work is geometrically assembled from Schweppes crates and painted timber to form a three-dimensional wall hanging that evokes an image of a rural environment.

As always in a depressed economic climate, items with good provenance will sell well. Ten registered bidders resulted in an intricate Robert Klippel (1920-2001) metal sculpture fetching Aus$60,000 (£41,100), more than three times its higher estimate. Klippel's witty and refined sculptures were also shown at Gallery A and he was known to be one of Lewis's favourite artists.

A passionate philanthropist, in her last years Lewis had given away more than 130 works from her valuable art collection to public institutions.

The buyer's premium was 22%. £1 = Aus$1.46

By Marika Clemow