British Airways B763 near London on Aug 12th 2014, smoke in cockpit

A British Airways Boeing 767-300, registration G-BNWC performing flight BA-103 from London Heathrow,EN (UK) to Calgary,AB (Canada), had just reached cruise FL340 when the crew reported smoke in the cockpit about 140nm northwest of London (almost over Liverpool,EN) when the crew reported smoke in the cockpit and returned to London Heathrow for a safe landing on Heathrow's runway 27R. Responding emergency services found no trace of fire or heat. The passengers disembarked normally.