By Christian Radnedge LONDON (Reuters) – British number one Cameron Norrie sailed into uncharted territory by reaching the fourth round at a Grand Slam for the first time with a comfortable 6-4 6-1 6-0 win over American Steve Johnson at Wimbledon on Friday. The world number 12, who joined compatriot Heather Watson in the last 16, next faces another American in Tommy Paul. Norrie becomes the first British man in five years to reach the last 16 at Wimbledon, the previous being twice champion Andy Murray. It was a much easier outing than his previous match when he was taken to five sets by Spania…