"To beat a Premier League club on their own patch is a big achievement," said Grayson.
"To say that it is bigger than the culmination of a whole season's work would be unfair but it is on a par.
"It is just as satisfying but it is not a shock because what we have done has not surprised me.
"The play-offs were a magnificent effort as we won 10 consecutive games and to achieve that at any level is a highlight.
"But this win caps a memorable 12 months in total for the club going back to the start of last season and hopefully it is the start of something."
