I have always assumed that Richard Williams named his daughter Venus after the planet she calls home. Certainly, no one at Wimbledon has a greater reputation for space cadetship, daftness, flakiness, a silly voice and a general air of being slightly out of step with us earthlings. And then I wonder if she’s the only sane one here.

There’s a story about Chris Evert in her pomp. She had just marmalised one of life’s quarter-finalists and, when they were both in the locker-room, the beaten one announced in a loud meant-to-be-overheard voice: “Thank God my happiness doesn’t depend on winning a tennis match.” Evert responded equally loudly: “Thank God mine does.”

We are taught that monomania is good. We accept the notion that only monomaniacs can cut it at the very highest level. We see any falling away from monomania as a failure of personality, a revelation of weakness, an admission of inadequacy. We take the driven ones, the obsessive ones, the blinkered ones as models for what a champion should be.

We respect such performers as Sir Steve Redgrave, for ever braving the icy river in a quest for perfection, we admire Daley Thompson training twice on Christmas Day to give himself an edge, we love Jonny Wilkinson kicking a million balls a day to keep the furies at bay. And we have the temerity to think that Venus Williams is a bit strange because she chooses to lead a comparatively normal life. Maybe it’s everybody else in sport that’s mad.

Yesterday, she beat the highly alliterative Tamarine Tanasugarn, of Thailand, over two meaty sets, 6-4, 6-3. She has yet to drop a set, she is into the semis and, despite the flaws in her game, maybe the only one who can stop her winning is her sister, Serena. It would be her fifth Wimbledon if she managed it; her seventh grand-slam singles title. She first won here eight years ago, and she’s still at it. No burn-out. Is it possible she is by chance doing something right?

When Williams père launched his daughters into the tennis world, he had this mad idea that they should be renaissance women, polymaths of sport, champions with their feet on the ground, winners with a hinterland. This is obvious insanity: tennis parents are supposed to din into their child’s minds that tennis is the only reality and that love is strictly conditional and dependent on victory.

Williams insisted that his daughter would seek to conquer the world in not one, but a thousand ways. So Venus went through high school rather than join the grown-up circuit as soon as she possibly could. She now runs V Starr Interiors (Ebone and Starr are her middle names), which does interior design: it is sad to note that New York’s failure to get the 2012 Olympics means that Williams’s designs for the athletes’ apartments will not see the light of day.

She also runs a fashion company called EleVen. She has a thing for poetry and art and Asian antiques. She’s read a lot of books, deeply dangerous things, avoided at all costs by most people in sport. She has announced that she now has ambitions in choreography; also in music, as producer rather than performer, although she fancies herself a bit on the guitar.

And yet she is a serial champion. She can wake up from her dreams about the perfect lighting on the Ming vase and the right way to make the belt sit on the hips; she can move away from her musings on art and the meaning of life and come out and play tennis as if the future of the human race depended on her victory.

She can turn it on — and off again. Afterwards she is an amiable flake with a silly voice again; the roaring, whacking demon we saw on court has somehow vanished. She still sticks to the tactic that has served her well throughout her tennis life: that of overwhelming. She was serving at speeds well in excess of 120mph yesterday, saving her fiercest stuff for when she was break point down, a thing that champions tend to do. “I really expect it of myself.” The shrieking was in good shape, the double-fister wasn’t bad and the forehand is, as it always was, rather like a horse I used to ride: beautiful, immensely powerful and ever-so-slightly uncontrollable, dangerous to both opposition and owner.

Tanasugarn pushed her hard in the first set, persistent and accurate, and had five break points in a single service game. Each time, Williams blasted her way out of trouble, first-serving and second-serving with passion and purpose. “I think I love power,” she said afterwards, and giggled.

She looked amazing under the clear blue Wimbledon skies: quite literally gleaming, the cheering sun picking vivid gold highlights from the generous acreage of skin revealed by her outfit. The abrasive, in-yer-face qualities she showed when young are muted now, her reluctance to follow tennis’s code of manners more or less gone. She even apologises when she pulls out of a serve these days.

But the appetite has not gone. It is just intermittent and now she is here, she is ready to win it again, while those who pursue their sport with the recommended single-mindedness can only wag their heads and wonder. “I don’t have anything to prove,” she said. “I’m very happy and blessed in my life.”