Thousands of sports fans braved the rain and cold at the Olympic Park in London Saturday as organizers staged the final test events ahead of the Summer Games. Student athletes competed in water polo, wheelchair tennis, field hockey and track and field events, watched by around 75,000 spectators. Saturday marked the first time the main stadium in the heart of the Olympic Park in east London was open to the public for an athletics competition. Organizers said about 40,000 people were expected to attend the official opening of the 80,000-seat Olympic Stadium Saturday evening. The final test events came after the British military performed a series of operations to test Olympic security, including flights over London by fighter jets and helicopters earlier this week. “This is the one big opportunity, particularly with the number of people we've got in the park, to test our venues, to test the park management, the security and tickets,” said Sebastian Coe, who heads the local organizing committee. With about 140,000 people attending test events over the past six days, the organizers also assessed the movement of spectators across the sprawling Olympic Park. “We are actually in a very good shape, but with a mountain of work still to do,” Coe said. Aside from complaints about the weather, few people had anything bad to say about the biggest day so far in the Olympic Park. Spectators, who bought tickets for the main stadium opening ceremony in March, patiently queued to enter the sports complex after airport-style security checks. Police helicopters flew over the park and armed police troops patrolled the area. “It's not a problem, really. It's much quicker than the airport and it's good to be checked because now we know we're safe,” said Simon Levy, a Londoner, who came to the Olympic Park for the first time Saturday with his wife and friends. Adrian Casy, a security guard at the Olympic Stadium, said Saturday's events were among the main rehearsals for the games, particularly in moving and managing the crowds of spectators from the Park and from one venue to another. With just over 80 days before Olympic competition begins, the organizers' main focus is the athletes. Test events are used to gauge reaction from participants to fine tune any changes ahead of the Olympics. More than 10,500 athletes from 204 countries will start moving into the Olympic village two weeks before the opening ceremony.