Several weekends ago now, I went to the Tate Britain to see the Chris Ofili and Henry Moore exhibitions. Both were good. I find sculpture difficult to “read”, as it were, although I found Moore’s stringed work very beautiful; the real highlight of his exhibition for me, though, was the central room of his sketches from the Blitz and from coalmines. The Ofili, similarly, wasn’t initially to my taste, but grew into a rather nice body of work, and the room of his blue paintings was wonderful; I enjoyed the catalogue of the Blue works I read later, although was disappointed to see how many of the Blue paintings hadn’t been selected for display.

But the best thing I saw in the gallery that weekend was a total surprise.

That surprise was David Hockney’s Bigger Trees Near Warter.

I glimpsed the painting through a doorway, not in its entirety, just part of it, already filling the doorframe and enticing me in. What greeted me on the other side was, in every sense, stunning.

Bigger Trees Near Warter is a huge painting, made of 50 canvases – 10 wide by 5 high – and, in this showing, duplicated on two adjacent walls of the gallery in scale replicas constructed out of fifty photographic prints. It dominates the room, filling your peripheral vision as well as your forward gaze.

(I enjoyed Hockney’s rational for making the painting so big – he didn’t want the Royal Academy to try to hang anything next to it, and so he ensured it would fill the wall it was intended for)

And, as the explanatory documentary running on a small television on the fourth wall explains, the artwork was only really possible because of modern technology.

Hockney’s a very technically savvy artist – something that often surprises people – and it was fascinating to watch him at work. The computer’s role in Bigger Trees was very specific – it enabled pre-visualisation of the larger work, showing how the initial sketches would be divide across fifty paintings, and by stitching together photographs of work in progress, hinting at how the artwork was developing. After all, there wasn’t nearly enough room in Hockney’s UK studio to hang all the canvasses.

But that was it: each canvas was still very much painted in the field, and the stitched image helped plan which canvasses to take out each day. It’s still very much a landscape painting made on location. I admired both the necessity of technology to the painting, and yet a lack of complete reliance on it.

Enough of the method, though, because even if you didn’t know that, it’s still a phenomenal work: subtle use of colour that’s unmistakably English countryside, detail in the tree branches that’s visible at a distance, but recedes as you get closer; a painting on such a large scale it never escapes your eye. It dominates you, keeps you in place, and then the shapes form into detail and draw your eye in.

I looked at this one image for a good while – longer than I’ve looked at any single painting for a long while. My eyes occasionally darted right and left to check that the facsimiles really were identical, and not variants; quiet and still in one of the gallery’s larger single rooms, awed, and glad to have followed my nose – or rather, my eyes – through that doorway. I’ve been a fan of Hockney for a while, but this was just magnificent; if you’re passing Tate Britain in the near future, it’s worth the detour to find. Words and photographs can hardly do it justice.