The grandson of Sigmund Freud died last July at the age of 88 while collaborating with the gallery on the show of 130 works of art, which includes his unfinished "Portrait of the Hound", the auction record-smashing "Benefits Supervisor Sleeping" and some moving paintings of his dying mother.

"Lucian Freud Portraits" documents the evolution of Freud's painting methods over seven decades from flat to highly textured and highlights his use of colour, light and detail in an effort to capture the core personalities of his subjects, many of whom were friends or lovers.

"Freud's portraits are the realisation in paint of a relationship between artist and model that has slowly developed over time behind closed doors," National Portrait Gallery curator Sarah Howgate said in a statement.

Gallery officials stressed that the show, sponsored by Bank of America Merrill Lynch, was not a mournful retrospective, but a celebration of his work and changing styles.

"Although many of his subjects have led complex lives, most of them - with the exception of a few public figures - prefer to hold on to their anonymity. Lucian Freud is a life represented in paint rather than a biographical retrospective," Howgate said.

The show is part of a countdown of events celebrating British culture in the lead-up to the London Olympics this summer and will be kicked off by a visit from British Prince William's wife, the Duchess of Cambridge, later on Wednesday.

Among the portraits in the show, which opens to the public on Thursday and closes May 28, is "Benefits Supervisor Sleeping", which was auctioned at Christie's in 2008 for $33.6 million -- at the time, a record for a work by a living artist.

The buyer was widely reported to be Russian billionaire Roman Abramovich, the owner of Chelsea Football Club, though this was not confirmed officially.

The painting, which is on loan to the gallery from a private collection, features the generously proportioned Sue Tilley or "Big Sue", an official at a centre for the unemployed who became a minor celebrity after posing naked for Freud.

Freud was fascinated by the subject's imposing physical presence and he created several portraits of her that came to be seen as a celebration of the female figure in all its forms.

Other subjects included fellow artist David Hockney, Freud's assistant David Dawson, his daughter Bella Freud, the fashion designer, and photographer Harry Diamond.

The paintings were loaned by public and private collections around the globe including the Tate, the Museum of Modern Art in New York and the British Council.

Dotted among the pieces are touching paintings of Freud's mother Lucie in her dying days, several self-portraits and "Portrait of the Hound", depicting Dawson and his dog Eli, which had been left in the artist's studio after he died.

(Editing by Estelle Shirbon and Paul Casciato)

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