With exactly one month until the Olympics get underway, London Mayor Boris Johnson has joked that the Olympic rings symbolise, amongst other things, chastity.

Speaking as a new set of rings were unveiled at London's Tower Bridge, the Mayor said the rings symbolise the Olympic virtues which include: " Exertion, competition, sportsmanship, courage, chastity, poverty".

He laughed the comments off, following them up by saying the rings are: "A great big invitation from us to the world."

The Mayor was accompanied by London 2012 chairman Lord Coe, and both watched as the rings measuring 25 metres wide and 11.5 metres tall were lowered into place above the River Thames.