I saw them yesterday, two of van Gogh's five remaining 'Sunflower' paintings (the other three are in Munich, Philadelphia and Tokyo) juxtaposed in the National Gallery. One resides there, the other is on loan, from the Van Gogh Museum in Amsterdam. It is the first time they have been displayed together in London for sixty-five years.

I'm no Sister Wendy. Nor do I count the decades since I studied Art History. But any painting will speak to anyone, if you stand there long enough.

We know that van Gogh was the first painter to use colour to reveal emotion; that 'Starry Night', to which Don McLean paid eternal homage, stands as a reflection of Vincent's mental torment towards the end of his life. I'd seen both of these 'Sunflower' paintings in their usual homes. Would I see more in them by viewing them side by side?

The visual variations are obvious. The explanations given as to how these were achieved make sense to the non-artist. But what struck me was the music in those canvases. You can almost hear the southern French fields in which they grew. There's a rustle and a hum about them. Through their luminosity leaks an awkwardness and insecurity that makes you gasp. There is terrifying darkness in all that light.

In a yellow house, Vincent painted yellow flowers in a yellow jug against a yellow wall. An explosion of sun, light and optimism. Beyond the odd dab of red, blue and green, it was fifty shades of the colour which least reflected his soul. A bouquet of barbed wire, hinting at the mania consuming him from within.

Two-dimensional canvases. Pictures. Impressions. This pair are worth millions. Why are they so valuable? Why do they matter? Because they exude more energy and more truth, perhaps, than any other painting you've ever looked at?

'Le Peintre des Tournesols', Paul Gauguin called his friend, with whom he had at best a fractious relationship. 'The Painter of Sunflowers.' We admire and respect Still Life because of the way it speaks of the relationship between mankind and the natural world. But we admire van Gogh for much more. There is humility in the simplicity of these paintings. An admission, possibly a spiritual one. We can observe, appreciate, reflect. We can put a flower in a vase and paint a picture of it. We can write a poem or a play or a novel, compose music inspired by it. We can dance to the tune of the sunflower, but we can never create it in the first place. You see?