I became completely and solely an insect — all eye. I flew from colour to colour, from red to blue, from yellow to green. Colours went spirally through my body lighting a flare as if a rocket fell through the night and lit up greens and browns, grass and trees, and there in the grass a white bird. Colour warmed, thrilled, chafed, burnt, soothed, fed and finally exhausted me.

This hyperbolic, rapturous description of the joy of viewing art appears in Virginia Woolf’s 1934 essay on Walter Sickert. The exhibition her character is so enthralled by was a 1933 retrospective at Thomas Agnews & Sons — an art gallery in Bond Street.

The description is undeniably dramatic, but, 89 years later and three miles further to the west, it is possible to understand how Woolf’s character reached such a state of excitement. Piano Nobile is currently home to the exhibition Sickert: The Theatre of Life, and any exhibition-goer might be forgiven for proclaiming “colours went spirally through my body lighting a flare”.

He’s telling Sickert “you’re not my Daddy”

Entering the first room of the gallery is akin to entering early 20th century Camden itself; paintings of music halls, grey-green nudes on metal bedsteads, and honest to the point of unflattering portraits fill the walls. This is the Sickert that most fans know and love. “Gallery of the Old Bedford” (1894-5) is one of the earliest paintings in the exhibition, but it is possible to see the seed of the later Camden Town paintings in its close-up depiction of everyday life and contrast between colourful interiors and an overwhelming aura of smoke, soot, and darkness. Many of his portraits from this period have a disquieting intensity: despite the differences in colour, subject, and changing style, both “Mamma Mia Poveretta” (1903-4) and “Œuillade” (c.1911) have a passion and forcefulness that is not altogether comfortable. Sickert was no society portrait-painter; he disdained the “wriggle and chiffon” school of Sargent, Boldini, and Helleu.

In “One of Madame Villain’s Sons” (c.1901-2), the boy’s eyes and crossed arms make a mockery of the painting’s provenance: Vanessa Bell and Duncan Grant bought the painting thinking it was of Sickert’s illegitimate son, but the art historian Wendy Baron has proved that the dates do not match up.  The boy’s glare and grumpy posture seem to answer this question without the need of biographies or books: he’s telling Sickert “you’re not my Daddy”.

It is paintings like this that have led to the (unfounded) rumour that he was Jack the Ripper

Perhaps the most captivating portrait in this part of the exhibition is “Chicken” (c.1914). It is impossible to beat around the bush: Emily Powell was no looker — her gap-toothed smile and wide-set eyes are by no means traditionally beautiful. But Sickert paints her with such energy, vitality, and life that she seems to be about to leave the frame and emerge from the wall.

A few of Sickert’s famous nudes make an appearance. “Mornington Crescent Nude” (1907) feels so quintessentially Sickert that it would almost be easy to pass over it, but the evocation of flesh in reds, blues, greens, and yellows deserves attention. “Nuit d’Été” (1907) is as compositionally and formally brilliant, but the woman’s splayed legs and semi-obscured face give the canvas an altogether more unnerving air. It is paintings like this that have led to statements such as “Sickert was a creep” and the ever-persistent (and unfounded) rumour that he was Jack the Ripper.

“The Studio: The Painting of a Nude” (1906) is slightly earlier than both of these two paintings, but Sickert’s achievement is arguably far greater. On first glance, it is the convincing fleshy-ness of the woman that strikes you: her legs and back are so faithfully rendered as to appear tangible. It is only when you realise that this is a painting of a reflection in a mirror that the mastery is even greater: the woman’s behind is reflected in one mirror, and the canvas is the other. In demonstrating his painting process — mirrors, paintbrushes, and all — Sickert has also demonstrated his complete control of perspective and composition. The man truly was a genius.

The exhibition is split over the two sides of the gallery. In the second half, we leave the Camden Town phase behind and enter the war and post-war years of “late Sickert”. This is the phase of Sickert’s art not universally appreciated. The last major exhibition of “late Sickert” was in 1981. Piano Nobile picks up some 40 years later, and shows the terms “early” and “late” are flawed; Sickert was an artist of constant change, exploration, and creation.

Perhaps the most poignant painting in the whole exhibition is “The Integrity of Belgium” (1914). A man in a blue uniform kneels astride the ground above a trench; his hands are raised to his face and holding binoculars to his eyes; his black leather boots look out of place in the mud and earth around him. Sickert had met Belgian officers in London and noticed their distinctly old-fashioned uniforms. The final painting juxtaposes their blue figures with a news-reel-esque background of the fields of World War One. Old is forced to meet new both on the landscape of war and in the landscape of painting — this is one of the first paintings where it seems Sickert has used photo-based source material.

Sickert existed beyond the confines of North London and beyond the earliest years of the 20th century

But whilst Sickert’s Belgian soldier is hopelessly out of sync with the modern theatre of war he has entered, Sickert himself was easily able to adapt to an artistic modernity that he was, in part, responsible for creating. His “Tiller Girls” paintings (1928) have a distinctly sixties, pop-art feel about them — indeed, Andy Warhol was a Sickert fan — whilst his other paintings have hints of Freud, Bacon, and Leon Kossof.

“Late” Sickert is not the dying production of an old man, but the radical experimentation of a continuing artist. It is easy to be disparaging of photo-based portraits like “Mrs Robert Van Buren Emmons” (1930) or “The Row” (c.1935) if one only ever expects the Camden-Town paintings of Sickert’s youth. The truth is that Sickert existed beyond the confines of North London and beyond the earliest years of the 20th century; it does him and his art a disservice to pretend otherwise.

The Piano Nobile exhibition also features a generous selection of Sickert’s drawings and etchings — some of which are surprisingly affordable given the rising value of Sickert’s work. His pen-and-ink works lack none of the vitality of his paintings and are a wonderful way to own something by such a brilliant artist.

Piano Nobile have succeeded in bringing together a veritable cornucopia of Sickert’s works from private and institutional collections, and in making ridiculous the division between “early” and “late” phases of the artist’s work. Sickert is not an artist whose career can be divided into Camden Town fame and then obscurity; he is a continued master of colour, flesh, and narrative. “When I first went into Sickert’s show, … I became completely and solely an insect — all eye.”