London has sent a giant set of Olympic rings down the River Thames to mark 150 days to the start of the 2012 Olympics.

Olympic rings, mounted on a barge, are positioned in front of Tower Bridge on the River Thames in London February 28, 2012.

The Rings on the River standing 11 metres high and 25 metres wide were due to travel down the Thames barrier past Canary Wharf and Greenwich.

The gates of the world-famous Tower Bridge were opened to allow the giant pass underneath. Mayor Boris Johnson and hundreds of flag waving children watched the event serenaded by a steel band.

The Rings finally returned to the 19th century bridge next to the Tower of London and then went into storage to re-emerge during Games' time as part of the 'Look and Feel' of London 2012.