By then, Paolozzi and Turnbull had already been influenced by the great modern masters in Paris whom they had met, particularly Brancusi, Leger and Giacometti. The Hanover Gallery in London spotted the original talent of the two Scottish artists, and sponsored a joint exhibition of their work, guided by the emergent writer and critic David Sylvester. This was in 1956. John Russell claimed (in his 1965 survey, Private View, in collaboration with Lord Snowdon and Bryan Robertson) that, 'In any history of British art since the war, William Turnbull would earn a place on several counts, as painter, as sculptor, as teacher, as ideas man to more than one generation of students'. In his painting of about that time he was strongly influenced by Barnett Newman, producing equally large canvases, now difficult to trace. The ICA's 'Young Sculptors' exhibition in 1952 was followed by the exhibition entitled 'New Aspects of British Sculpture' at the Venice Biennale, also in 1952, under the aegis of Sir Herbert Read in the British Pavilion, and this enabled William Turnbull truly to take off in public and critical esteem.

The current new show at Waddington Gallery reminds us, however (and most importantly now), that Turnbull has always been both a painter and a sculptor. He had left Dundee to join the Slade School of Fine Art in London as a student and painter in 1948. The sculpting of the first standing figure of many that he produced in 1955 paradoxically led him to abandon the figurative in painting. The sculptures seemed then to focus on special qualities of silence, peace and stillness, ten years after the noise and dramas of war - Turnbull had been involved as an RAF pilot in World War Two. At this point in the show there are particularly relevant examples, including a tall bronze figure, sacerdotal and with an evocative tilt of the undersized head (1955) and conversely a bronze 'idol'. Clearly a female goddess, displaying a succinct and formal economy of execution (1956), this emblematic and totemic bronze, almost five feet high, well represents that fertile period in the artist's work. 'Screwhead' (1957) stands apart from the previous figures, discrete and enigmatic.

From 1959, 'Strange Fruit' shows an emergent minimalism, finding the poetry of true materiality, where a solid bronze rounded piece is set on a rectangular block of York stone, also focusing on that element of stillness. These sculptures stand in marked contrast to the paintings in the exhibition, which Turnbull also executed during the later 1950s: clearly he is forging a dominant intellectual direction and these all form an appealing, even arresting contrast. Seldom are the sculptures and the paintings viewable in close proximity to each other. Does the painting inform the sculpture, or is it the other way round? This is the riddle of Turnbull's work, and a brilliantly provocative interaction. Large, dark abstract paintings suddenly expand into a lyrical fusion ('Untitled', 1957) where red and yellow areas are separated by a thin horizontal demarcation of purple. It was about this time that Turnbull met and married Kim Lim, a Chinese sculptress.

Turnbull's emphasis in both the early paintings and the sculptures on applied relief, working to a very light depth gives an interesting shared characteristic to the works in both media. 'Black Painting' (1957) reveals the markings of the palette knife in creating a series of both vertical ridges. Both 'Figure' (1957) and 'Idol 2' (1956), and indeed the third sculpture of 1956 shown exhibit this scoring of the surface. For 'Figure', Turnbull pressed ordinary corrugated cardboard lightly in place in a wet plaster, which created the impression of striated, textured seams. The effect of the fluid plaster, fossilising as it could be said, into bronze deepened the prevailing aura sought by Turnbull, of stillness and permanence. 'Strange Fruit' (1959) brings together what seems to be a primordial cranium, burnished and weathered, onto the rectangular bock of simple and untextured York stone.

There seems no question that Turnbull's wartime experience as a flyer cast a formative thrall over his subsequent painting. 'Painting 20' (1959) acknowledges a balancing chrome work, not just in a flattening of the planar perspective (as from a cockpit) but bringing about a pervasive stillness to counteract all movement. In 'Painting 20', two planes split into one looming arc, perhaps denoting a steeply climbing aircraft in the sky. '3' (1960) shows the equivalent of a widely climbing vapour trail. In reality, such traces would have been firmly impressed on the artist's mind at the time, when flying high. At Waddington Galleries, this carefully selected range of works, specifically from the years 1946-63, allows a clear appraisal and analysis of the interaction between painting and sculpture in the hands of a single artist, in early career, who was skilled and later uniquely distinguished in both media. The early perceptiveness of the late David Sylvester, and indeed of Herbert Read, indicate how a critic can encourage a balanced duality in output, preceding any enforced concentration by the artist on one medium against the other. The recent exhibition of Turnbull's sculpture at Tate Britain (2006) unfortunately avoided this conjunction, which was endemic to Turnbull's oeuvre, even though, at the Serpentine Gallery in 1995, Sylvester had helped to emphasise the importance of this duality.

Nearly a decade later, Waddington gives us an insight that further consolidates this essential richness and duality in Turnbull. He is best seen in this way; a highly distinguished and talented artist of his post-war generation, and one with many lessons for historians, critics and also students. What is admirable is to experience today in one artist a productive output of work, with interaction between painting and sculpture. As this exhibition shows, Turnbull is an adept master at both, and it must be said that his work demands rather greater international recognition. Waddington Galleries are also to be congratulated for putting forward, rather than suppressing, the artist's own agenda. Sometimes, museum curators fear to go where long-established commercial galleries insist.

Michael Spens