Lucien Freud’s golden eggs for the duchess

A postcard-size oil painting of four eggs on a plate, measuring just 4in by 6in, is expected to sell for £150,000 – or more – at Sotheby's in London next month. They're not just any old eggs, though. The auctioneers said "the exquisitely beautiful painting" was given to the late Deborah, Dowager Duchess of Devonshire – known as "Debo" – as a gift by the painter Lucian Freud in 2004.

Deborah (nee Mitford), the youngest of the famous six English sisters, in 1941 married Andrew Cavendish who became the 11th Duke of Devonshire in 1950. She was, Sotheby's said, "famed for a somewhat eccentric pursuit for a society beauty, a passion for chickens" which she kept at Chatsworth – the family seat in Derbyshire and also at Lismore Castle in Co Waterford, the Devonshire family's Irish home.

Although her portrait was painted by leading artists (including Freud), arguably the most interesting and famous image of her is that by photographer Bruce Weber showing her in a ballgown feeding her chickens. Chickens feature prominently in the various volumes of her published memoirs including Counting My Chickens (published in 2001) and Home to Roost: And Other Peckings (published in 2010).

She and Freud were close friends and she once recalled: “Good old Lu. I take him eggs every time I go to London.”

Her husband died in 2004 after which she was styled Dowager Duchess of Devonshire (her daughter-in-law becoming the 12th duchess) until her death, last year, aged 94.

Sotheby's said she had kept Four Eggs on a Plate, wrapped in cloth from the artist's studio, in a blue box with a note which reads: "Box & rag he uses in his studio containing the painting of 4 eggs given me by Lucian Freud autumn 2002, DD". The lot in the auction includes the painting, the note, the artist's cloth and the blue box.

Oliver Barker, Sotheby's senior international specialist in contemporary art, said the painting demonstrated "Freud's tremendous virtuosity as a painter, transforming a simple subject into a work of extraordinary power" and represented "a friendship between an artist and a duchess". It is not known what she thought of the painting.

Her obituary in the Daily Telegraph noted: "Despite living in a house overflowing with masterpieces by such artists as Rembrandt, Veronese, Murillo, Poussin and Reynolds, the Duchess always maintained that Beatrix Potter was her favourite artist".

Four Eggs on a Plate by Freud is estimated at £100,000-£150,000 in Sotheby's contemporary art evening auction in London on July 1st.