Of all the mind-boggling graffiti I have seen, somewhere near the top of the list must rank Fergie the Greatest and MUFC, artfully stencilled in many colours on the Great Wall of China.

How the soccer hooligan got away with it still leaves me wondering, although if caught he — or she — as a Man U fan could have pleaded insanity. (This is not funny — Ed.)

From graffiti to more formal murals is but a short step, and from the Neanderthals of 60,000 years ago, through the Renaissance with its Holy Trinity of Leonardo, Michelangelo and Raphael, you can fast forward to the vibrant abstract patterns the Ndebele women of South Africa paint on their huts to enjoy works that have informed, educated and delighted us.

And the tradition continues apace in East Africa, from that giant okapi browsing the outside of a hotel in Kigali to the creations of the Kenyan Bhupi Jethwa, who with the tag Wise Two has decorated buildings from Adelaide to Bogota, from New York to Nairobi.

Jethwa’s work is already well known in Nairobi, with murals in Jericho and Maringo estates, and at the Ibis hotel in Westlands. But for the first time he has held a solo show in Kenya, called Time Travel, at the Circle Art Gallery in Nairobi.

There he has painted the gallery’s largest wall with a mural some 2.6 metres high by almost eight metres long. Alas, it cannot be for sale and after the exhibition ends, on October 26, it will be painted over ready for the next exhibition.

So why did he not create the mural on an outside wall, for keeps? The reasons are twofold: First, the gallery’s lease forbids any permanent alterations to the building’s exterior, and second, Jethwa has learnt to celebrate the transitory nature of his art.

“I want my work to be relevant only to the moment and place in which it was created, and therefore permanence is not an issue,” he told me.

Permanent or passing, I admire the gallery for its imagination and courage in offering visitors such a site specific, immersive experience.

The mural is probably best described as a portal into lost civilisations, an attempt to link the present to a glorious but distant past.

Based primarily on the rich iconography of cultures of the Aztec and Maya of what is now Mexico, it reflects the artist’s recent working visit to Central America. The geometrical structure around the main image acts as a curtain pulled back to reveal a glimpse of both past and present.

Decorated with the complex linear designs found on ancient temples, it frames a stylised figure floating above a brilliant red pyramid set against an azure sky. A vertical red line rises from the pyramid to pierce the figure, suggesting the link from past to present, the travel through time of the exhibition’s title.

In addition to the mural are 10 acrylic paintings on canvas, each a more convenient 150cm by 90cm, in which the artist runs us through the gamut of his obsession with ancient civilisations by riffing on his two main motifs of masks and trees — the masks both disguising other cultures while triggering access to their hidden worlds; the trees symbolising the cycles of life, of feast and famine.

What these canvases show us, apart from an abiding concern with meticulous finishing, is that in this work more than most, scale matters.

Murals more than seven metres high and covering the gable ends of buildings have a powerful presence. With their robust designs and vivid colours they could, as they say, stop a bus.

Oddly enough these and his acrylic paintings reproduced at postcard size (in the excellent catalogue that accompanies this show) have an almost equal presence, even allowing for the fact that any painting gains in intensity through reduction.

But the canvases, for me, slip between the two extremes and lack visual validity as easel paintings. The staring masks and sprouting greenery have a psychedelic appeal straight from the Sixties, and strike me as ideal for printing on T-shirts or, better still, for laminating onto surfboards.

For there is a Beach Boys vibe to this show… carefree, falsetto harmonies that tell not so much of honouring old cultures, but of sunshine, sand and patterns plundered from the past for a blinding, salt-in-your-face moment; one that begins well with Good Vibrations but is liable to end suddenly with a nose dive into the spray and a tangle of seaweed around your head.

To see Wise Two at his best, relish the mural at the Circle and then go surfing — but on the Net, not on the ocean waves — to see the other magnificent murals he has created around the world.