Wanderers earned their first Championship point and arguably deserved all three after an impressive display against Watford at Adams Park.
The Blues had the better of the chances throughout but fell behind to Ismaila Sarr's header, only for Anthony Stewart to level from Joe Jacobson's corner.
A blistering first half display should have seen Wanderers take at least a one-goal lead into the break, as they outclassed their former Premier League opponents with a combination of tenacious midfield play and fast-tempo attacking.
First Ben Foster produced a fine save down to his left to deny Kashket’s effort from eight yards, and the keeper flew to his right to hold a stylish effort from Adebayo Akinfenwa which curled towards the top corner.
Akinfenwa then planted a golden chance over the bar following excellent build-up play from Curtis Thompson and Kashket, with Horgan then being denied by a last-ditch tackle in the box after Watford had had a goal disallowed for handball.
Foster played to the same tune at the start of the second period, firstly denying David Wheeler’s first-time volley with an excellent stop down to his right, and then thwarting Akinfenwa from close range.
And then came the sucker punch. Watford hadn’t come close to looking like scoring, but broke the deadlock with an all-too-simple header from Ismaila Sarr following an inch-perfect cross from the right.
The same player came close to a second with a low drive which was well saved by Ryan Allsop as the visitors finally began to settle into the game with a goal’s advantage behind them.
But Wycombe stayed resolute and got their reward. Thompson did well to win a corner and Joe Jacobson’s delivery was as inviting as it gets for Anthony Stewart to power home a header, giving Foster – finally – no chance.
Akinfenwa headed a tough chance wide after impressive wing play from Horgan before Watford made two subs to introduce Nathaniel Chalobah and Glenn Murray from the bench, and then Akinfenwa’s flick released Kashket who shot early as the angle narrowed and Foster cleared with his boot.
Uche Ikpeazu, Fred Onyedinma and Alex Samuel came off the bench in the final 10 minutes and the latter played a part in a talking point when Joe Jacobson’s corner landed in the net, only for the referee to spot a tangle between Samuel and Foster.
Then Murray missed a golden chance to win it in stoppage time, firing narrowly past the far post with the game’s final chance before the referee called time to signify Wanderers’ first Championship point was secure.