A British Airways Airbus A320-200, registration G-EUYD performing flight BA-2596 from London Heathrow,EN (UK) to Verona (Italy), was climbing out of runway 09R when the crew stopped the climb at FL100 reporting a burning odour on board and decided to return to London's Heathrow Airport. The aircraft landed safely on Heathrow's runway 09L about 20 minutes after departure and taxied to the apron with emergency services in trail.