By Martyn Herman GHENT, Belgium, Nov 30 (Reuters) – Incredibly, improbably, Britain will end the year as world champions of tennis after beating Belgium in the Davis Cup final, but that grand title rests squarely on the shoulders of one extraordinary player. The 115-year-old event is held up as the sport’s most prestigious team competition, but never has one individual been so instrumental in winning it as two-times grand slam champion and Olympic gold medallist Andy Murray was this year. The 28-year-old Scot won all three of his matches in Ghent, two singles and a doubles with brother Jamie in between.