Justine Henin trails a cloud of unhappiness. Such is her nature. She has a face like one of those Northern Renaissance madonnas overcome with the sadness of life. Playing tennis is a serious business, but she does at least allow herself a smile when she wins. The transformation is startling and it came yesterday afternoon, and in full measure: she had just dispatched her third-round opponent, Elena Vesnina, of Russia, 6-1, 6-3.

Henin has had a sad life, so it’s just as well she is so good at winning tennis matches. Her mother died when she was 12, she became estranged from the rest of her family and had no contact with them for seven years. She married and, with a dreadful inevitability, it all went wrong and she was divorced in January. Now she is Miss Henin again, no longer Henin-Hardenne, and she is punctuating her sadness with bouts of tennis of miraculous quality.

She has had a rapprochement with her family, but even that was born of sadness. Her brother was involved in a near-fatal car accident and such things tend to clarify one’s priorities in life. The brother came out of a coma to find his long-lost sister at his bedside.

Henin has the air of a woman who expects sadness, but that is not to be confused with a sense of defeat. She doesn’t care for defeat. She is No 1 in the world and collected her sixth grand-slam title in Paris three weeks ago. As you would expect, though, her career has not been all sweetness and light.

She has had problems with knees, back, hamstrings. She is prone to illness – any virus seems to lay her out. Last year she quit on her stool, like Sonny Liston, in the final of the Australian Open. She was a set and 2-0 down to Amélie Mauresmo and had a poorly tum, but the tennis world was not overimpressed with the idea of walking out of a grand-slam final.

But she was quite splendid yesterday. She has made a conscious decision to play more aggressively at Wimbledon, feeling that she was too predictable against Mauresmo when she lost the final at Wimbledon last year. Well, why shouldn’t she? She moves beautifully and has a sublime touch anywhere she happens to be on the court. She volleyed like a good ’un yesterday and served at times in excess of 110mph.

How on earth does she do it? There’s not much of her. She looks in need of the famous all-day breakfast in the press canteen and a box or two of Belgian chocolates to follow. She is not quite as slight in person as she seems on television – a reversal of the usual rule – although still frail enough. But she gives the ball a hell of a whack. It’s all in the timing, the technique, the coordination.

Henin is built more like a marathon runner than a racket player, but she is a joy to watch on court. The classic one-handed backhand is as lovely a shot as you will see in the game and, as you would expect, she covers the court better than anyone. She is seeded No 1 here and is likely to meet Serena Williams in the quarter-finals, so don’t miss that one.

Henin is in superb form and will take a bit of shifting. Her game is a pure one, based on intelligence rather than power. She is a confirmed nongrunter, which is a bit of a relief. On court, she confines herself to an occasional muttered “ Allez!” She doesn’t do theatrics, but in a quiet way she likes to be the boss of the court.

Yesterday she made Vesnina feel like an intruder. The well-known perversities of No 2 Court affected her not at all. She carved up the Russian with neatness and precision and after that she permitted herself the day’s smiling ration. She said afterwards that she was enjoying herself out there, and we must take her word for that. Certainly, the way she was hitting the ball spoke of a real relish for the business.

Henin’s temperament is much like the Wimbledon weather this year: generally gloomy but with occasional, brilliant outbreaks of dazzling sun, the more glorious for being so unexpected. In her press conference, she was asked by some poor fellow with a lot of space to fill whether she had any talents outside tennis. And for some reason, she found this wonderfully amusing: “I sing so well! No . . . I would love to sing well.” And the sun came out and blessed us all in that windowless room.

But what about winning the whole damn thing, Justine? “That would be great, but that wouldn’t make me more happy for my real life after tennis.”