Heading into the night they knew one point would be enough to top the conference and the replacement hooker's score was the Wanderers' fourth of a breathless playoff for top spot.
Things didn't start well for them either, falling behind after failing to gather the kick off. From the resulting scrum defenders strayed offside and Tim Taylor kicked the hosts into the lead.
Good work in midfield from GJ van Velze and Luther Burrell almost played Will Hooley in but having quelled that threat, a punt forward was again dealt with poorly by the visitors and after a penalty for holding on, Gloucester mauled over the resulting lineout.
Yet while another Gloucester grubber through ended in a yellow card for Noah Cato's obstruction, it was the visitors who looked spurred on and off the back of a solid scrum, Tom Stephenson was well supported by van Velze who fed Alex Day for the score.
Still, Gloucester stuck with the tactic of putting boot to ball and with advantage being played, a high ball bounced kindly for Ian Clark in the dead ball area and Hooley couldn't prevent a second Cherry and White try.
The game was starting to ebb and flow and after a fine, fast break from Ben Nutley the ball went quickly through the hands to Cato whose try went some way to making up for his yellow card.
Again Gloucester cancelled out the score quickly though, Clark on hand to slide over on the left, doubling up on the stroke of half-time and ensuring an 11-point buffer for his side as the teams turned around.
With the slope now in their favour, the Wanderers played most all of the third quarter in Gloucester territory, but it took some 24 minutes of pressure and a touch of class from Tom Collins for a just reward.
From a quick lineout the young winger stalled his run and dinked a chip and chase perfectly over, booting once more before haring over. Game now well and truly on, the Cherry and Whites looked to be tiring but on their first foray into the Wanderers' half, the hosts wrapped up the bonus point, driving Elliott Stooke over.
With the teams separated in the league table by just one point on points difference, the Wanderers went in search of a crucial bonus point - which looked to be all but up when they knocked on close to the home line.
The twist was yet to come though and when the hosts engaged early at the scrum, Ryan Glynn fed the rampaging Williams who proved unstoppable from 15 metres out.
With the point in the bag, Hooley converted for a second and despite defeat, the Wanderers came out better off in the league standings with the Aviva 'A' League to move into the playoff stages in December.
2mins GLOS Pen Taylor 3-0
11mins GLOS Try D'Apice Con Taylor 10-0
16mins GLOS Pen Taylor 13-0
19mins WAND Yellow Cato
25mins WAND Try Day Con Hooley 13-7
28mins GLOS Try Clark 18-7
34mins WAND Try Cato 18-12
40mins GLOS Try Clark 23-12
HALF-TIME GLOS 23 WAND 12
64mins WAND Try Collins 23-17
75mins GLOS Try Stooke Con Taylor 30-17
80mins WAND Try Williams Con Hooley 30-24
FULL-TIME GLOS 30 WAND 24