Rory McIlroy shot a seven-under 65 to move to 12 under on another brilliant day at Augusta for the defending champion Credit : Mike Blake/Reuters Rory McIlroy is six shots clear and enjoying the biggest-ever lead at the halfway point of the Masters. A remarkable seven-under 65 featuring four closing birdies in a row has taken him to 12-under and with more Augusta history tantalisingly in focus. What a performance and what a defence this has been. Talk about London bussing it. After taking 17 attempts to don the Green Jacket, the Northern Irishman has left the field in his wake and has another exclusive club to join. Of course last year, as he ended his 11-year major drought, McIlroy became just the sixth player in history to complete the career grand slam. Now there is an even more elitist set beckoning. The only three players to retain the Masters title are Jack Nicklaus, Sir Nick Faldo and Tiger Woods, the latter the most recent 24 years ago.…