Her mother, Sue, battled with the Football Association, invoked the Equal Opportunities Commission and wrote enough letters to start an alphabet factory. The FA, living up to its ponderous reputation, was immovable. "They came up with feeble excuses like problems of changing rooms. It seems ridiculous that girls can still play a tactile sport like rugby but can't play 11-a-side football with boys after nine years old," Sue said.
So Harriet, who lives in Twickenham, took up rugby - and rapidly became a star at that. Sadly, it looks like her prospects with London Scottish are limited, too. Though she is an automatic choice for the club's junior team, she has reached the ripe old age of 11. That means she will have to switch to women-only rugby next year. RFU rules, you understand.
How good is she? Well, Harriet was the only girl in a London Scottish squad of 26 that has recently returned from a Scottish Borders tour, playing centre against junior clubs from Melrose, Jed-Forest, Kelso and Selkirk. She was not there as tea maker and kit washer, either. Norrie Jackson, the chairman of London Scottish's mini-rugby section, says: "It's uncanny. She is an amazing player, totally committed and unquestionably one of our best tacklers. She can compete perfectly well against boys."
Harriet herself is disappointed but not distraught. She has, after all, plenty of other options. She is national triathlon champion for her age group, she ran in last month's Flora London mini-marathon finishing 148th, and she's in the England under-11 girls' chess squad. She's in the school netball team, and fancies her chances at shot putt and long jump. Quite simply, whatever she turns her hand to turns into trophies, medals and badges.
By now you have probably built up a mental picture: tall for her age, an Amazon with an incipient moustache; compensating for her ungainliness and shyness with sporting aggression. Dogging her steps, parents who never quite made it themselves and are determined to do so through their daughter.
Wrong, wrong, wrong, wrong and wrong.
The biggest shock is to discover that Harriet is tiny: 4ft and not many inches. This little thing terrorising boys a head taller? The secret may be that she is also wonderfully self-assured without being arrogant or precocious. The acting maxim - never work with kids and animals - is a good lesson for journalists, too. Eleven-year-olds who can discuss training programmes, motivation and ambitions are rare indeed. Her parents have such confidence in her ability to handle a press interview that they leave her alone (though mum hovers in the kitchen).
There is no genetic reason why she should be a sporting natural. Her parents teach special needs, not PE. Sue's involvement runs to an occasional gym session while her father, Simon, Loughborough-trained, she manages a school football team, does the occasional triathlon and has completed a dozen marathons with a best time of just under three hours - scarcely the DNA of superstars.
Harriet's sporting career started at three, when she entered a fun run. A year later, she showed an aptitude for gymnastics and won a few trophies, but gave it up (aged nine) because it took up 12 hours a week - time she wanted to spend on other ventures.
At school, she proved so good at football that she was an automatic choice for the team (she has even got a trophy for Man of the Match). She played midfield, scored a few goals and never had any problems about being a girl in a field of boys. "I changed in the same changing rooms. It wasn't a problem. I think the boys actually behaved themselves better because there was a girl around."
Afterwards she played a little with Fulham's under-16 girls squad but found that when you're only nine, a 15-year old is like someone from Brobdingnag. "They were really big," she recalls.
When her younger brother Adam went for a trial with London Scottish juniors, she tagged along, liked the game and got involved. Bumps and bruises do not worry her. "Even though it's a contact sport, people tackle you to get the ball, not to hurt you," she says. Her mother is less sanguine. "Her legs get covered in bruises and she had some heavy falls in the Scottish games, but it doesn't worry her. Personally, I would be devastated if she came home with a broken nose or a cauliflower ear."
Then came triathlons. When her dad took part, she joined in, liked that too and last year won six of the seven races in her age group to become national champion. "She is naturally very competitive in everything she does," her father says. "She doesn't need to be pushed. She even keeps a training diary."
Almost every evening of Harriet's week involves athletics, swimming, cycling, running or rugby training, though on Fridays she is involved in drama, and some Saturdays there is a chess match. "We're glad that she's got a balance between the physical and the cerebral," says her mother. "But ultimately, it's her decision about what she does."
Harriet has not settled on one sport yet. She enjoys them all. Ask what sports she doesn't like and she thinks hard. "Hmm, can't think of one." This summer, she hopes to play cricket. She would like to try skiing, or even ski-jumping.
Her Christmas presents were sports kits and a pair of roller blades. Toys? "It means I have to find time to sit down and play with them." Her bedroom is filled with trophies and pictures of her competing. Idols? She names Simon Lessing, Britain's triathlon champion, not Take That.
She is even remarkably mature about the future. No vows of Olympic medals or being the first woman to play for England in the World Cup: she likes the idea of physiotherapy, and wouldn't mind being a woman referee. A laudable ambition, but you feel she may be underselling herself. Another Daley Thompson? I made sure and got her autograph (for my daughters, you understand).Reuse content