25/09/2015 12:55 BST | Updated 24/09/2016 06:12 BST

David Hockney: Early Drawings

David Hockney: Early Drawings is a feast of a show and a fine way in which to introduce Waterman's eponymous gallery's new grand location in the heart of London's Mayfair

"Ink drawings are unbelievably unforgiving. There's no room for error," proclaims gallery owner Offer Waterman as he lauds the technical skill and emotional impact of some of David Hockney's early portraits. If there was a mistake, and they were rare, a gentle use of the scalpel would be enough to disguise it.

David Hockney: Early Drawings is a feast of a show and a fine way in which to introduce Waterman's eponymous gallery's new grand location in the heart of London's Mayfair. It's situated opposite Sotheby's at 17 St George's Street, where the William Morris and Co textile showroom was once housed . "A bit of Chelsea has come to Mayfair," says Waterman.

The exhibition comprises 55 works drawn from 16 private collections around the world and centres on the gallery's own works, 30 of which are for sale. They span the 1960s and '70s.

For Sleepy Kas (above), from 1967, is a typical example of the kind of intimacy Hockney achieves in pen and ink, capturing the essence of his subject, in this case his art dealer John Kasmin. It's achieved in minimalist fashion that draws the focus and allows the brain to fill in the rest.

This portrait, from Kasmin's personal collection, is also typical in other ways. The annotations at the bottom of this and other works enhance the close relationship and say much about the artist himself.

Hockney never went anywhere without a sketchbook and capturing his subjects asleep, and not therefore moving, was perfect modelling time for him. What's more, as with artists like Lucian Freud, he was at his best when working with people he knew well.

Among these were his lovers. The exhibition is laced with erotic portraits of such as Gregory Evans and his first great love Peter Schlesinger. Peter, Le Nid de Duc (above) from 1971, is a beautiful work that holds a certain poignancy because the couple's relationship was on its last legs by then. Schlesinger is looking away, red-eyed and disengaged.

Hockney was open about his homosexuality even when gay rights did not exist and to be gay was socially unacceptable. His brazen and unashamed manifestation of his sexuality within his drawings showed a brave willingness to take a principled stand. In this way, this exhibition becomes not just a study of artistic brilliance but also of a kind of moral crusade.

It reveals a consistent steeliness that had seen him become a conscientious objector over his National Service, just as his father had been during the Second World War. He fought the RCA's decision not to let him graduate in 1962 after he'd refused to write an essay, saying he should be judged only on his artworks. They relented.

Offer Waterman relates a story about how Hockney's stash of American gay men's magazines was once confiscated by British customs at his arrival at Heathrow on the grounds of their "inappropriateness". He took his case to the highest echelons of government. The magazines were duly returned. Even today he is still campaigning, as a high-profile figure in the pro-tobacco lobby.

Hockney's overtly sexual depictions weren't primarily aimed at propagandising gay rights - it was the way he lived his life that he was expressing. Yet they became part of a collective striving for a sexual revolution that gripped the late 1960s.

Indeed that spirit of optimism and self-expression captured by the effervescent Hockney, with his trademark dyed golden hair and round broad-rimmed glasses, is evident in his now familiar iconography. Among these is the figure of Celia Birtwell, one of Hockney's set of friends who in many ways encapsulated that decade.

Celia, 1972 (above) is one of three portraits of her in the exhibition. It's the first time it has been on show and is one of the items on sale. Other familiar icons are those chairs, the cigarettes, beds and a foreshadows of a future passion, the inevitable swimming pool that so defined his early years in Los Angeles.

Hockney's travels were a feature of his early career. Such was his reputation that in 1963, only a year after leaving the RCA, the Sunday Times sent him to Egypt from which he returned with innovative drawings in coloured crayons, one of which is in the exhibition. They were shelved owing to the assassination of John F. Kennedy and not published until 2012.

Hotel Luxor, from 1978 (above) shows a return to Egypt. Hockney's fondness for vivid colours that exude warmth and the use of blank white paper to invoke heat owes something to Impressionism.

Indeed, one aspect of David Hockney's early drawings that soon becomes apparent is his fondness for mixing styles. We also see elements of pop art, of expressionism, nods to Picasso and cubism and abstraction. Later, we were to see him continually innovate with the use of acrylic, computers, photography, the iPad and 3-D printing to name but a few.

"This mixing of styles was not a question of him finding his feet," maintains Offer Waterman, "He has taken multiple branches throughout his life and continued to innovate."

This is an intimate exhibition in both style and substance with nothing of the grandeur of his recent monumental works. The early drawings are a reminder of how David Hockney first set out on the road to becoming one of the most influential British artists of the 20th century and perhaps the best loved.

David Hockney: Early Drawings runs at the Offer Waterman Gallery from 25 September - 23 October 2015. The exhibition is a collaboration with the Paul Kasmin Gallery, New York, to which it will transfer from 3 November - 1 December 2015.

All images are copyright David Hockney and are used with the permission of the artist and gallery.