John Constable: A kingdom of his own by Anthony Bailey

Portrait of the artist as St Francis of Assisi

In general, the very beginning is not a very good place to start when it comes to reviewing books. With Anthony Bailey's new life of John Constable, though, there's nothing else for it.

Here are Bailey's opening lines: "The lane slopes gently from the village to the river, grassed ridge in the middle and wheel-ruts to either side... On the right the trees in the hedge are thinning out. Dark furrows in the ploughed field beyond [converge] before vanishing together in the early morning sun. A pheasant whirrs over a fence to a pasture where cattle are grazing. A bird's nest can be seen; the hedge needs re-laying." The prose seems familiar, as if you've read it before. Then it comes to you. You haven't read Bailey's words, you've seen them: in the Tate, in a picture by Constable called Fen Lane.

As with his earlier book on Vermeer, Bailey's genius lies in finding a literary equivalent for his subject's style. He doesn't just describe Constable's pictures, he writes them, each spare word like a stroke of the artist's brush. At the end of John Constable: A kingdom of his own, you feel less that you've read a biography than that you've seen a self-portrait - or maybe heard Constable's voice, soft and unadorned like his painting. Poema pictura loquens said Plutarch: poetry is talking pictures. Swap poetry for prose and you get Bailey's drift.

Now, you may say that this identification with his subject is unlikely to result in even-handedness, and you'd likely be right. But who cares? The Constable that emerges from Bailey's book is so utterly nice that you want to believe in him, that his is the hand behind those scenes on the Stour.

Among the sharper thorns in Constable's side was Turner, whose paintings of Venice and mythical heroes thrilled academicians to his rival's cost. A year older than him, Turner was elected to the Royal Academy nearly three decades before. Unbowed, Constable went on doing what he liked best, which was landscapes rather than "the shaggy posteriors of Satyrs". When Turner submitted a Dido and Aeneas to the Academy in 1814, Constable sent in A Ploughing Scene. As ever, RAs massed, cheering, before the first and ignored the second. Still, writes Bailey, oozing love, "[Constable] said that he would rather be the author of his own landscape with the ploughman", and carried on undaunted. While Turner set off for Italy, Constable stuck to Suffolk. "I should paint my own places best," he said, and did.

In Bailey's tender hands, nothing is safe from Constable's niceness. His friend, Charles Leslie, recalled that the artist's fondness for children "exceeded... that of any man I ever knew", that his babies "might be seen as often in their father's arms as in... their nurse's". He was, says Bailey, "always a giver: alike to poor musicians, impoverished painters, hard-up East Bergholt folk and young women selling flowers." Another friend saw the painter give a shilling to a crying girl with dirty knees. He was even kind to mice. One lucky rodent in the kitchen at 35 Charlotte Street - chez Constable in the 1820s - "got very fat... but then Constable would put rinds of cheese out for it". "Two sparrows came into the house and let themselves be caught by Constable," writes Bailey. "Birds liked him."

So, clearly, does Bailey, which accounts for the rough treatment meted out to Maria Constable. While her husband is Francis of Assisi, Maria is a pantomime cow. Jealous of Constable's old friend, Johnny Dunthorne, she insisted that one of them had to go. Johnny went. Maria rewarded her husband-to-be by forgetting to write to him - "thinking hurts my chest," she moaned - complaining that he wrote to her too often and then, when he cut down on his letters, not often enough. Given that she was dying of TB, Bailey's treatment of Maria seems a bit harsh. But then no-one likes Other Women, which is how he sees her.

The picture this lovely book paints is of a Constable as warm as The Hay Wain. The difference is that The Hay Wain has a dark side which Bailey ignores in its maker. Artists' biographies are tricky things: you can't explain a painter's work by his life. That said, Bailey glosses over Constable's political conservatism, obvious in his work and by no means his most endearing feature. For all its Suffolk idyll, The Hay Wain shows a place where rich men live in castles and poor men at their gates. It was a world Constable saw fading, and mourned. This doesn't detract from his kindness to mice and children, but it does make him more complex than this book perhaps allows.