The study raised new questions about the teaching of history after it found that 11 per cent of the British population believed Hitler did not exist and 9 per cent said Winston Churchill was fictional.Unfortunately, they don't spell out the survey methodology (wording of questions, categorisation of answers) clearly enough to tell whether some of these are truly howlers or just worst-case interpretation of reasonable answers:
Some 57 per cent think King Arthur existed.... Almost one in two believe William Wallace, the 13th-century Scottish resistance leader played by Mel Gibson in his film Braveheart, was invented for the silver screen.Does "I believe that the Arthur myth may have been rooted in historical fact" count as "I believe King Arthur was real"? Does "I think the portrayal of William Wallace found in Braveheart was almost pure fiction" count as "I think William Wallace was invented for the screen"?
(There's also the possibility that people were fudging their answers for comedy value anyway. According to the survey, 3% of the adult UK population believes that the Battle of Helm's Deep really occurred... but this is the same country in which 0.75% of the population claim to follow the Jedi religion.)