Yesterday's tremendous triumph is a fantastic reward for an enlightened Chairman, who was prepared to give an untried 35-year-old his first opportunity in management following the departure of former boss, Ray Lewington a year past March.
However, after securing Championship survival during his first few weeks in office last season, even Simpson has been surprised by the speed of progress made by the club this term, although the belief of his manager in achieving Premiership status was never in question as he recalled to Sky Sports News earlier today.
''It's just starting to sink in, you look at the newspapers in the morning, see the headlines and realise what this man Boothroyd said 12 months ago about actually getting there, he's achieved that.
We started this season as relegation favourites, we asked him and said 'Aidy where do you think we will finish?'
He said minimum play-offs and chasing automatic. We did all take a breath but he said from day one that was his ambition.
They (supporters and press) were surprised but we'd done our homework, we'd had a good recommendation about him.
He was outstanding in interview, he's been preparing himself for many years since his career ended at 26.
We had absolutely no doubts when we got him on board. We were getting on a very special train when we got on board, but we didn't realise it was an express train."
Simpson admits planning for next season will have to start almost immediately as a budget for new players has already been set in place.
'We've arranged to meet and the budget was set whether we were in The Championship or The Premiership.
We know what money we've got, Aidy has a good idea of the players he wants. We're going to be sensible.
We're not going to spend millions and millions on one player. We're going to find hungry players that will improve the squad. It's obviously Aidy's choice.
We started this season as favourites to go to League One, no doubt they'll be quoting us to go down already. But, watch this space.''