12-year-old Lucy Fuller from Essex was the lucky visitor, who received a surprise welcome from Seb Coe, Chair of the London 2012 Organising Committee.
Lucy was visiting with her family, who were making their way to the Aquatics Centre to see ParalympicsGB swimmer Ellie Simmonds compete in the 400m Freestyle heats.
Seb Coe presented Lucy with some special London 2012 gifts, including a signed commemorative book, a mascot and a bracelet, commenting: 'It was fantastic to meet the Fuller family today and I was delighted to be able to present them with some special London 2012 gifts. It’s great to see so many families on the Park.'
Lucy said: 'It’s been so great being here on the Park today, watching the action in the Aquatics Centre and meeting Lord Coe. I’ve just got back from holiday so this is the best way to finish the summer before I go back to school. I can’t wait to tell all my friends that I was the three millionth visitor.'