Great works: Thames Painting: The Estuary (Mouth of the Thames) (1994-5) by Michael Andrews

Avaledictory to painting? Yes, perhaps. To a degree. Michael Andrews was undergoing treatment for cancer when he was working on this near-hallucinatory vision of a landscape at the sea's edge, and it does indeed feel like a glimpsing of something at the rather chilling outer limits of human experience, some kind of a mysterious embodiment of a slipping away from life into the unknowable dissolution of whatever follows after.

Its aerial viewpoint is magnificently dizzying. It seems to wheel and to lurch beneath our gaze. We look and look far down into it. We almost feel ourselves to be in the equivalent of the cockpit of a helicopter which suddenly jerks its tail end, precipitating us forward. It seems to induce that degree of vertiginousness. It is a great vortex of a fraction of landscape at the edge of water, the one perpetually squaring up to the other, that seems to suck in our seeing.

This finished canvas is only a fraction of Andrews' labour on this final piece. Andrews fussed and fussed over his work. He was a man who believed in the virtues of meticulous research, and if one day you decide to go over to Chichester to see this painting in the flesh at Pallant House Gallery (having first checked before you leave that it is not out on loan), you might induce them to show you one of the preparatory drawings for this piece called "Study for Thames Painting: The Estuary (Mouth of the Thames)", probably made in 1993. This particular page from his sketch book contains ink drawings of the crocodile movement of shifting sands, together with various tiny, scribbled notes to himself about what to put where, and why, such as these: "Lugworm digger?" (beside figure of a bending man) or "Bring the water in?", the second as a challenge to himself.

Is the final work abstract or figurative? Figurative, surely. In fact, by a whisker. Why so? Because we would perhaps feel less inclined to categorise it as figurative painting at all were it not for those tiny figures on the shore, with their rods pointing out to sea. Otherwise, with its grainy, slicky, mixed-media surface, it could be an expression of mood or rhythm tout court. Those figures tell us otherwise. They almost shock us by their presence because we are quite slow to spot them, and when we do so they are so arrestingly, so Brobdingnagianly tiny, and by being so they seem to embolden and widen and aggrandise the rest of this slithery off-cut of estuarial terrain, which seems to slither and shift into ever more indefinite and undefinably variable shapes even as we stare down at it in wonderment.

Their smallness, their insignificance, caught as they are between the push of this shifting land at their back and the welter of engulfing sea that they face, alarms us. For all that, they are the witnesses, the doughty, undeterred go-betweens.

It is in part a homage to Dickens, this painting, the painter's favourite writer, whose characters also haunted this patch of ground. It has the slightly sinister mood music of a scene from Dickens. Human beings can seem to teem small in Dickens too. There are always so many of them, like a million chattering termites. The figures do something else that is very important too: they impose scale on the painting. Thanks to their presence we can judge, immediately, the actual – as opposed to imaginative – size of what exactly it is that we are looking at.

The painting also nods in the direction of Turner, and the way that he dealt with the strange, indeterminate meetings of sea and sea's edge, the shocking changes of colour, how the fumy turbulence of the weather can change the shape and the reality of everything visible within the blink of an eye. The fact that we know it to be an actual piece of terrain at the mouth of the Thames heightens our sense of drama.

If we were to find ourselves comfortably settled in the knowledge that this were an experiment in abstraction, we would regard it more coolly, more dispassionately and analytically altogether. The presence of these homunculi persuades us to feel more.

About the artist: Michael Andrews (1928-95)

Michael Andrews, born in Norwich, was a publicity-shy British painter in the figurative tradition, who studied under William Coldstream at the Slade School of Art. He famously captured the world of Muriel Belcher's Colony Room in the hedonistic Sixties. Generally speaking, he worked slowly and meticulously, and had relatively few exhibitions during his lifetime. His talents also encompassed acting: he played the part of a deaf-mute in Lorenza Mazzetti's film Together (1955).