The Olympic Stadium in London has been officially opened ahead of this summer's Games in the English capital.

Around 40,000 people witnessed nine-year-old East London local Niamh Clarke-Willis help Sebastian Coe press the button to release hundreds of balloons into the London sky.

Coe said that the track had been designed to be one of the fastest on the planet, commenting: "I think we have got a crowd-pleaser in the stadium. I think we have also got technically one of the fastest tracks that has ever been laid."

The Games' opening ceremony takes place on Friday, July 27.