In the Fifties, Britain had its own painter to rival the abstract expressionists of New York. The star of a prime time show on ITV, he counted Pablo Picasso and the Duke of Edinburgh among his collectors. His name was Congo, and he was a chimpanzee. Two million viewers tuned
Art goes ape: How Congo the Chimp conquered the art world
"As humans, we share 99 per cent of our DNA with chimpanzees, and I was fascinated to see whether they share our artistic impulse, too."
His investigations began by singling out Congo, the most exuberant of the zoo's chimps – on grounds he'd probably be the most exuberant artistically, too. Seated in a baby's highchair, and with materials laid out by Morris on a table before him, Congo set to work. Though several pieces were created on camera, most were done in privacy.
"He started out just making random lines," says Morris. "However, over time, he showed great control over the marks he made and how he organised them. Rarely did they stray beyond the edge of the picture."
Living up to artistic stereotype, Congo had a hot temper. When he felt a work was finished, he'd fold his arms and refuse to make another touch. Likewise, if anyone tried to stop him in full flow, he'd have a tantrum: screaming, tearing his hair out and stamping feet.
Morris tried his artistic experiment with a few other chimps over the years but insists Congo was "the Leonardo of the ape world". Not because he painted a simian Mona Lisa but because he was a special talent.
"His most remarkable feat was thematic variation," Morris says. "He loved making a fan pattern – this was the basis of much of his work. Gradually, though, he began making variations on the fan, sometimes adding a spot in the middle; sometimes adding a second, smaller fan; sometimes painting an inverted fan (where the lines radiate from top to bottom rather than vice versa).
"He was developing visual patterns and, like any artist, making conscious aesthetic choices as he did so."
For Morris, this proved how deep-seated the artistic urge is: though it finds maximum expression in humans, it exists among chimps too. Sadly for Congo, his artistic heyday didn't last long.
He lived apart from other chimps, in a luxurious cage in the zoo's television unit. However, aged five, after viciously attacking Morris's secretary, he was deemed a danger to humans and returned to the monkey house. In 1965, aged 10, he contracted tuberculosis and died.
Morris went on to write the international bestseller, The Naked Ape, in which he argued that, beneath the veneer of sophistication, humans are fundamentally just apes.
It is with reluctance he's parting with his Congos: at 91, he recently moved to a smaller home, in Ireland, and hasn't the space he had before. The works range in price from £1,500 to £6,000 ($3,000 to 12,000), and the Mayor Gallery says a third have already been sold, since the show's opening on Tuesday.
Looking back on his Congo experiment, what does Morris think is its legacy? "Quite simply, the birth of art. With one talented chimp, we witnessed the germ of artistic creation as we know it."
It's a legacy, in other words, to go ape over.