She followed in the footsteps of her mother Princess Anne, a former Olympic horsewoman who received the flame in Athens last week along with David Beckham.
A champion equestrian herself, Zara is hoping to qualify for the 2012 Games.
"It would be amazing to be part of it, to actually go to an Olympic Games. Everything is hitting home now the torch is here. The buzz has started.
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There was a slight hitch when Zara momentarily lost her grip on the torch because her mount Toytown got scared by the noise from the gas-fired device.
But the Queen's granddaughter kept her cool, recovering to complete the circuit.
Toytown stopped racing last year because of injury, but his devoted owner brought him out of retirement for the big occasion.
"This one is for him," she said, adding it meant he could still do something for the Olympics.