Olympic logo unveiled on Bankside

The design, rolled down the side of Tate Modern as London bid leader Barbara Cassani watched from the Millennium Bridge, is based on the Thames which is portrayed as a ribbon in the colours of the five Olympic continents.

The ribbon weaves its way through the letters of London 2012, showing the flow of the river round the Isle of Dogs alongside the Lea Valley where the games will be hosted if the bid succeeds.

Andy Stanfield of Kino Design whose design won the £10,000 fee said: "We chose the Thames because it flows through the centre of London and is the point at which many of the city's waterways and communities meet.

"It is also symbolic of the people from all over the world that flow in and out of London, defining its style, personality and vibrancy."