Stern's remarkable oil painting Portrait of Freda Feldman in Basotho Hat, provides an insight into the enduring friendship between the artist and Feldman, her closest friend and protégé. The painting is accompanied by the Basuto hat worn by the sitter who, like Stern, was known for her individualistic style. Marion Arnold,in her seminal work Stern, Irma Stern: A Feast for the Eye, notes: ''Freda Feldman was well known in Johannesburg for her collection of hats, a fashion foible she shared with Irma Stern.''

20905_1 Irma Stern, Portrait of Freda Feldman in Basuto Hat, 1943

Strauss & Co senior art specialist, Emma Bedford commented: ''It reveals their common interest not just in fashion and stylish hats and clothes, but also their shared passion for African culture and their ingenuity in forging an aesthetic that draws on both African and European inspiration.''

Strauss & Co has sold seven of the highest-priced Stern paintings in South Africa, and set the South African record for a work by Irma Stern – also the record for a work of art sold at auction in South Africa – when Two Arabs sold for R21 166 000 (£926 915) in 2011.

The Johannesburg auction also includes a number of high-quality artworks by other leading South African artists. An impressive selection of oil paintings and watercolours by the great master and innovator of South African modernist landscape painting, JH Pierneef, will feature among them, as will two still lifes by Pieter Wenning and a pair of oils by Gerard Sekoto.

20992_1 Jacob Hendrik Pierneef, Die Bosveld Huisie

20450_1 Pieter Willem Frederick Wenning, Still Life with Peacock Feather and Buddha

20314_1 Gerard Sekoto, The Casamance Dancers and the River Seine, 1975

A striking still life painting of sunflowers by the flamboyant and controversial Russian-South African painter Vladimir Tretchikoff has already generated considerable excitement. The work hung for many years in a tea room in Pietermartzburg. Press clippings from the time include one in the Sunday Tribune, which noted how its owner, who ran the tearoom ''says it attracts a lot of interest – it's so lifelike that many customers want to touch the flowers, painted with a raised technique, to see if they are real.''

20470_1 Vladimir Griegorovich Tretchikoff, Sunflowers, 1959

Among the contemporary works on show are works by Robert Hodgins, William Kentridge and Peter Clarke, all of which are sure to attract international interest. Strauss & Co's Important South African and International Art will take place on 23rd May, 2016. Search the sale on Barnebys here.