THERE IS an Arabic saying: "I against my brother; my brother and I against my cousin; I, my brother, and my cousin against the stranger."

Yesterday afternoon, after their father, Richard, had flown home to Florida saying his job was complete, Venus and Serena Williams teamed up to plot the downfall of Nathalie Dechy and Casey Dellacqua in the doubles quarter-finals. When they had dusted down the French woman and the Australian in straight sets, the two left to think about how they would conquer each other.

The Williamses may be best friends as well as sisters but when they step on court it has always been business. Siblings, companions and hitting partners, they know more or less everything that's worth knowing about each other - frailties, strengths, loves and dislikes - and if there is any one thing that will determine the outcome of today's Wimbledon final, the first they have played against each other for five years, it is what is going on in their heads.

In that respect, little sister Serena has been the dominant force in Grand Slam finals and has lost just one of their past six meetings. She is also the player with more Grand Slam titles: eight to Venus's six.

Serena's personality is also different; she is the sister most likely to blurt out what she really thinks, while Venus is the calming, reflective side of the act.

There is an instinctive agreement between the two when they are interviewed together. Serena does all the talking except when some gravitas is required, and then Venus steps in.

"Actually I think we've gotten closer in the past few years," said Serena. "We talk about a lot. We talk about everything more now than we've done in the past."

Venus, 18 months older, went on to explain they now know their roles better than they did before.

She is the elder sister and she holds an elder sister's view of Serena. Perhaps that goes some way toward explaining why she has lost more often than she has won in their duels. Venus has always had to look out for her little sibling, so how does she go about changing her mindset and tear her to ribbons on Centre Court?

"We definitely rely on each other's advice even more. You know I was a big sister," said Venus. "I was kind of like 'you never make mistakes'. So then I think I put pressure on her to be perfect too. Not that I'm perfect. I'm just really like a nerd.

"She wasn't exactly that way, so I think we both know our roles in the relationship and we support each other."

There are really no comparisons in the sporting world where someone so close is also a greatest rival. Everybody has a view on the two players and their family, while Elena Dementieva's comments on Thursday, to the effect they decide before the match who is going to win, don't really stand up.

It is also because of the Williamses' close relationship with each other and their family that they are seen as distant from the rest of the players on tour.

The respect for them in the locker-room is grudging, and though the two often speak about humility, both regularly say things that could be construed as arrogant.

"We're just going for history. We definitely want to be a part of it and stamp our names in those pages," said Serena in a largely uninformative press conference following their doubles win yesterday.

Neither of them could recall the last time they played a doubles match and then had to prepare for a Grand Slam final the next day, but they did point out that playing the doubles was good practice for the singles.

Serena will certainly go into the match the hungrier of the two; she has not won a Major since the 2007 Australian Open. And Venus will want to retain her title as she did back in 2001.

"I think the opponent hasn't gotten any easier, that's for sure," said Serena talking about her sister. "So it's going to be a battle again. I'm going in there playing the best player - and I hope for her the best player - so it's going to be a tough match."

Neither sister has looked at the tapes of their previous meetings at Wimbledon. Neither has thought much about what she is going to do. Nor have they spoken to each other at all about the final.

But there is little mystery about what shape the meeting will take. It will be big and loud and both will be going for winners off almost every ball. There will be volleys of searing shots and many errors.

The two of them have tidied up parts of their game and improved certain areas but stylistically they have remained the same, with heavy ground strokes and big serves. In the majority of their matches over the last two weeks, the two have simply overpowered their opponents.

Venus, particularly, has been serving heavy and this week delivered the fastest serve ever recorded by a woman at Wimbledon, a 127mph ace to finish her match against the Spanish qualifier Maria Jose Martinez Sanchez.

"It's going to be a battle again. That's just how it is," said Serena. "We're used to it. We think that we're finally getting the results that we deserve."

VENUS V SERENA
28 AGE 26
6ft 1in HEIGHT 5ft 9in
11st 6lbs WEIGHT 10st 7lb
7 SEEDING 6
7 WORLD RANKING 6
18,556,982 CAREER MONEY 19,266,700
6 GRAND SLAMS 8
6 GRAND SLAM RUNNER-UP 2
36 WTA TOUR TITLES 31
W 2000, 01, 05, 07 BEST WIMBLEDON W 2002, 2003
7 HEAD TO HEAD 8

MEN'S SINGLES
Semi-finals: (2) Rafael Nadal (Spa) bt Rainer Schuettler (Ger) 6-1 7-6 (7-3) 6-4, (1) Roger Federer (Swi) bt Marat Safin (Rus) 6-3 7-6 (7-3) 6-4.
MEN'S DOUBLES
Semi-final: (2) Daniel Nestor (Can) Nenad Zimonjic (Ser) bt (9) Lukas Dlouhy (Cze) Leander Paes (Ind) 7-6 (7-4) 4-6 6-1 4-6 8-6.
WOMEN'S DOUBLES
Semi-finals: (16) Lisa Raymond (US) Samantha Stosur (Aus) bt (1) Cara Black (Zim) Liezel Huber (US) 6-3 6-3, (11) Serena Williams (US) Venus Williams (US) bt Nathalie Dechy (Fra) Casey Dellacqua (Aus) 6-3 6-3.
MIXED DOUBLES
Semi-finals: (1) Mike Bryan (US) Katarina Srebotnik (Slo) bt Igor Andreev (Rus) Maria Kirilenko (Rus) 6-4 6-2, Bob Bryan (USA) Samantha Stosur (Aus) bt Jamie Murray (Brit) Liezel Huber (US) 2-6 7-6 (7-1) 6-4.
ORDER OF PLAY
Centre Court (2.0pm): (6) Serena Williams (US) v (7) Venus Williams (US), (8) Jonas Bjorkman (Swe) Kevin Ullyett (Zim) v (2) Daniel Nestor (Can) Nenad Zimonjic (Ser), (16) Lisa Raymond (US) Samantha Stosur (Aus) v (11) Serena Williams (US) Venus Williams (US)