The biggest oohs and aahs on the entertainment scene this winter were nothing to do with the ‘He’s behind you …oh no he isn’t’ of pantomime. They were the collective gasps of astonishment from 21,000 spectators at Kempton Park on Boxing Day as Thistlecrack, a novice steeplechaser in only his fourth race over the big fences, took on two previous winners of the King George VI Chase and beat them hollow.