The SAS, the Special Air Service, was created 75 years ago during World War 2 in the deserts of North Africa. The brainchild of David Stirling, the tactics they employed were quite revolutionary for the time. Major Mike Sadler was their desert navigator, able to guide them across featureless terrain so they could carry out their missions. Now aged 96, Mike is the last survivor of that original generation of the SAS. For Newsnight, he gave Ben Macintyre what he says will be his final interview.