Thye are rich, focused, self-reliant and they may feel they owe nothing to anybody. However, there is a growing feeling in SW19 that the Williams' sisters are duty-bound to produce a competitive, thrilling women's final on Centre Court today.

The sisters have not played a grand slam final for five years but these occasions have hardly been missed.

A clash between Serena and Venus normally attracts the description of "flat".

The conspiracy theories abound. They are whispered in press rooms, alluded to in player interviews, before being hastily retracted, and form much of the background noise to the final.

There is not a jot, not an iota, not the merest shred of proof that the Williams sisters come to any arrangement about matches. There is ample evidence, however, that contests between them are rarely compelling. This may be purely down to the emotional difficulty of one sister playing another. This, though, would be strange given their competitive instincts.

It may be that their styles can cancel each other out.

But the stage should be set for a grand final today. The Williams are under pressure to produce. There are indications that the family is aware of this burden. Venus was contemptuous on Thursday of any suggestion that who would win Wimbledon could be "a family decision". This was advanced by Elena Dementieva, the beaten semi-finalist, before being withdrawn.

Both sisters yesterday were guarded with the press in the wake of reaching the women's doubles final with victory over Nathalie Dechy and Casey Dellacqua 6-3, 6-3. Pressmen prowled around the question of motivation. The sisters played a blocked return to every inquiry that breathed danger.

Could they inform the world of any occasion when they played doubles together the day before a Grand Slam final?

Venus: "I d on't know."

Serena: "I don't know."

Richard Williams, the father and coach of both players, has left for home in Florida. Did he say anything before he left? Both sisters declined to reveal anything substantial. Had either of them watched matches they played against each other at Wimbledon?

Venus: "No."

Serena: "No."

This reticence may be forgivable when the sisters are smarting against unfounded allegations.

It becomes absurd when Venus can be asked what she is reading at the moment and replies: "I don't remember the name of the book."

So what are the chances of a final to remember?

This is in the hands of the sisters. It has the potential to be fantastic contest. But, then, so did the previous finals between two women who have 14 Grand Slams between them.

There is no question that Venus and Serena have deserved to reach the final. They have simply overpowered and outplayed everyone placed in their way. Their seedings were ludicrous given their achievements, particularly on grass. They have refuted any perceived slight with a series of brisk victories.

Although strong and athletic, there are enough differences between the sisters to provide a final of contrast. Venus, lithe and lean, has a serve that would grace the men's game. She can crank it up to a regular 125mph. She moves well behind her service when the occasion demands and his all-round game is solid, if not spectacular. The champion endured uncomfortable sets against both Naomi Cavaday and Anne Keothavong in the early rounds but she has gone through the tournament without conceding a set.

Her sister has been less assured and survived an examination by Zheng Jie of China in the semi-finals. Serena, though, has been regularly untroubled as she has steamed through to the final. Although bigger and bulkier than her sister, Serena has a slower serve. She is also more likely to try to slow the game by mixing drop shots and slices across court. There is enough in the styles and class of the two players to make this a Wimbledon of the highest quality.

Venus was upbeat about the prospects: "I think this is what we have been aiming for. We haven't reached this in a few years now. It's great that it happened."

Both sisters have written themselves indelibly into the annals of tennis. "I won my first Grand Slam almost 10 years ago and Venus very soon after that," said Serena. "So this is like we're just going for history now, trying to make the history books."

They have a chapter each in those books. It would be wonderful, though, if they could both gain a joint writing credit for the production of one of the greatest women's singles titles in the modern era.