In 1926 British climbers Andrew Irvine and George Mallory died while climbing Mount Everest. After Mallory's body was found six years ago, many critics suggested his clothing offered little protection against the extreme weather on Everest. But new analysis and reconstruction of the clothes suggest they were designed and tailored to be very effective against the cold - perhaps even better than modern synthetic fibres. Quentin Cooper investigates. Producer Julian Siddle