This restlessness permeates not just individual images but the shape of Cockrill's painting output. Works from the last 10 years are the subject of a fulsome and energetic retrospective at the Royal West of England Academy in Bristol. Even within this timespan, which represents less than half of his career, there is an extraordinary diversity of temper and style. Richly troubled landscapes in organic hues at one end of the show jar with hermetically abstract linear configurations in unearthly colours at the other. The same relentless force of nature which spawns life and terminates it seems to keep Cockrill on the move, preventing him from settling down comfortably into his own genre or style.
While this makes for an exciting body of work, it hasn't helped Cockrill's reputation. Despite wonderful handling of materials, an unquestionable painterly authority, the admiration of fellow artists (Paula Rego and John Hoyland among them) and the confidence of dealers and collectors, the lack of a trademark idiom has deprived him of success. Part of the problem is that he only arrived on the London scene in the early 1980s, starting his career afresh. Twenty years before that were spent in Liverpool, where he was well-known as a realist, installing huge billboard-like portraits of casual passers-by in Lime Street Station (a project funded by the Arts Council) and painting urban landscapes with deadpan photographic precision.
Dissatisfaction with that led to a decisive break. First there were violently choppy, neo-Expressionist figure paintings inspired by visits to the National Gallery, often dealing with mythological subjects about the battle between the sexes (they were exhibited in the Dusseldorf Kunstmuseum in 1985). These gave way to landscapes charged with a similar sense of disturbance and edginess. A series titled Song of the Earth justified the allusion to Mahler because, like his music, a gorgeous lyricism learned to live with strange abrasions and unsettling dissonances.
Cockrill is probably best known for such landscapes. At the time he was represented by the Bernard Jacobson Gallery which was at the commercial forefront of the 1980s revival of interest in the British romantic tradition, trading in such figures as Bomberg, Lanyon and Hitchens.
Cockrill's work related to these forebears, along with Nash and Sutherland, and fitted the ethos of the critic Peter Fuller who argued, in Ruskinian terms, for a modern landscape painting embodying spiritual yearnings. Cockrill's landscapes take an unsentimental view of nature; his landscape, like that of his own childhood in North Wales, is post-industrial, scarred and brooding. His painting is both tempestuous in its rough handling, and infused with hope in its richness and affirmative colour. For those after "redemption through form" (Fuller's catchphrase), Cockrill looked positively messianic.
This period was a highpoint for Cockrill. His works sold well, and Margaret Drabble wrote a monograph about him. And yet, perhaps precisely because of his association with Romanticism, he must have been perceived in some quarters as suspect - conservative if not anti-Modernist. The Tate has still to buy its first Cockrill and the Arts Council hasn't supported him since he left Liverpool. His former city, however, has not forgotten him.
In 1995, he was the subject of a full-scale retrospective at the Walker, which owns his tremendously ambitious and involving series of elliptical canvases from 1990, the Seasons. Within these suggestively egg-shaped canvases, a bustle of forms - pods, seeds, flaming hearts, loops, leaves, crystalline cellular structures - seem on the brink of becoming harbingers of symbolic meaning but jealously guard their potency.
These four pieces dominate the first gallery of the West of England Academy as once again the regions take up the cudgels on Cockrill's behalf. Bristol's RWA, an architectural marvel with its wonderful 19th century galleries, has a lively and courageous exhibition policy which deserves national recognition.
An artist who struck such a rich vein in his Seasons would have been justified in sticking with it, exploring subtle variations and turning the private iconography and lexicon of marks and gestures into his trademark style. But Cockrill moved on, questioning the voluptuousness of his own facility in extreme form by adopting wooden MDF doors as his support and - a graphic acknowledgement of implicit violence - "drawing" over the surface of the panel with an axe. Disappointingly, these Entrances of 1991 are excluded from the Bristol show. Instead, the curator, Ann Elliott (formerly of the British Council and Sculpture at Goodwood) concentrated on his most recent work, which has taken a turn towards lyrical abstraction.
But this is not such a sudden jump, as the show demonstrates. Cockrill is not so much stylistically promiscuous as dialectical: once he has followed one course, he always counteracts with a kind of opposition, although one that grows out of an unexpected aspect of his previous work, all of which informs, at some level, the synthesis which constantly beckons. Out of Entrances came the series Wheat, which gradually lost its symbolic literalness in a series called Generation. In these, an amorphous shape, within which nestle organic growths and landscape vistas, floats against a bright, almost garish monochrome ground.
It was here that a new kind of mark introduced itself. Detached from the rest of the composition, lasso or anchor-like forms provide some kind of commentary on the rest of the scene. As marks they are elegant, lyrical and spontaneous. This pulled up short viewers who thought they were used to the sumptuous Expressionism of his 1980s landscapes. In his latest series, Elements, dense webs of different coloured line evoke wateriness or fire. Seen on their own they look at first like 1950s salon abstraction, or some ironic, retro comment about such material, but in relation to Cockrill's private language and development they are a challenging dialectical statement. It's tantalising to imagine what's next.
Maurice Cockrill is at the Royal West of England Academy, Bristol, to 19 September. The exhibition will be shown in reduced form at Purdy Hicks Gallery, London, from 25 September to 17 October