The prized bravery medal of a naval officer who died trying to save trailblazing pilot Amy Johnson has emerged for sale.

Lieutenant Commander Walter Fletcher dived into the freezing water fully clothed after Johnson's aircraft ditched in the Thames Estuary in a snowstorm in January 1941.

Johnson, the first woman to fly solo from England to Australia, was never seen again.

The mysterious cause of her crash and death fuelled speculation that continues today. Some experts believe she was killed by the boat sent to rescue her.

Lieutenant Commander Fletcher, who had leapt into the sea from an armed trawler in a desperate bid to rescue her, was pulled unconscious out of the water suffering from exhaustion and hypothermia.