Giant Olympic rings have been installed at Heathrow Airport to greet competitors and spectators as they arrive in London for the Games.

A military marching band in their ceremonial red coats and bearskin busby hats played rousing music as the rings were officially unveiled on Wednesday.

London Games CEO Paul Deighton said: "37 days to go, we are ready to welcome the world."

The rings, which are the same size as a double decker bus, will be the first glimpse athletes and sports fans get of what is in store at London 2012.

Officials insist problems with lengthy queues at Heathrow border control have been ironed out and an extra 500 staff have been provided by the Home Office to help deal with the expected extra 600,000 visitors.

The incredibly busy hub of Heathrow already operates at 99.2 per cent capacity.