Met Police also won again so the Rocks’ lead at the top remains two points, but their goal difference is now two better than that of their rivals.
This win, inspired by Prior, who has 33 league goals to his name, also means the Rocks are guaranteed at worst second place, which would mean being at home in any play-off semi-final or final they have to play if they fail to finish first.
The Rocks could secure the title at home to Worthing on Monday (3pm) but will only do so if they win and the Met Police slip up. More likely is that the race will go to next Saturday’s final games.
Prior scored three second-half goals to add to his first-half strike before Dean Maynard wrapped up the scoring to give Bognor a thoroughly-deserved win.
A near full-strength side was in attendance at Bourne Park, with Dan Beck and Perry Ryan returning from injury and started on the bench. Michael Birmingham started his two-game suspension and so watched from the sidelines. The Rocks veteran will also miss the Easter Monday clash against old rivals Worthing at Nyewood Lane.
On a very dry and dusty pitch and against a team whose oldest player was 24, Dan Royce worked with James Crane down the right inside the first minute. The full-back’s cross from deep sailed over the bar.
Royce tried to find Luke Nightingale with a through-ball but it ran too far after Tim Bond was solid to stop the quick Hicham Akhazzan down the other end.
On four minutes Bond’s back pass slowed up on the sun-beaten turf and almost led to Ryan Golding scoring but Craig Stoner was fast out of his goalmouth to block the shot.
Bognor filed forward and a bouncing ball over defence saw the intuitive Prior get on the end of it, but his volley from the edge of the area was easily saved.
Conor Wilkins swung in a pinpoint right-sided corner for Prior to head towards goal. Akhazzan was on the line to block. The ball hit his leg and flicked across his body to hit his hand and a penalty was awarded by the linesman as the referee wasn’t sure.
The referee went to his pocket and produced a red card for Akhazzan, though many thought it was fairly harsh. Up stepped Prior to convert low into the bottom corner with just ten minutes on the clock.
The Brickies did have the ball in the net on 13 minutes, but this was after Ryan Cooper’s foul throw and it was ruled out.
Crane surged forward to cross for Prior, who with only the keeper to beat, first miscued a shot then forced a save from Matt Reed who blocked with his body. The resulting corner from Wilkins again fell to Prior, but the striker headed well wide.
Crane clattered into Ishankie Charles in his own half when he slid in a fair tackle and went to ground. Slowly he got up and returned to the action.
The hosts had a good spell in the middle of the first half.
Sam Collins lofted the ball goalwards but Stoner was there to gather before Jaie Nuttall could get anything on it. Golding almost got through once again but Crane tracked back to pass to his goalkeeper to clear.
On the half-hour mark Prior was tripped by Paul Semakula 35 yards out. Ben Johnson’s free-kick was poor and sailed out for a goal-kick.
The Rocks tried their best to pass the ball along the turf. Royce cut the ball inside to Crane but the full-back’s cross was headed away by Jack Hooper.
Prior pulled the ball across for Nightingale but the forward blasted well over from the edge of the area, hitting it on the rise.
The ball was bouncing all over the place but Nightingale beat a defender only to be caught offside.
Kane Wills, who had another solid game, set Johnson on his way down the left. The winger swung a cross in for Prior but Hooper headed clear.
In a rare attempt for the hosts, Charles shot from a tight angle inside the box but failed to hit the target, sending it flying well over the bar.
The final attack of the half was by the Rocks as Johnson stole the ball off Nick Reeves but his cross was cleared.
A good start for the Brickies saw them have some decent opportunities from kick-off. Six minutes in, a lofted pass forward towards Nuttall bounced kindly for Stoner, who gathered.
Then Nuttall crossed into the area for Hooper but his first-time shot flew wide.
Johnson fed Nightingale with a chipped pass but he was stopped by the offside flag - much to the dismay of the travelling support.
Johnson smashed a deflected shot straight into arms of the grateful Reed before the same player teed up Matt Whitehead on the overlap down the left - but again the goalkeeper came out on top.
On 64 minutes Nightingale held the ball up well for Johnson to cross into the area. The ball was cleared and a corner kick given. The kick, taken by Johnson, fell to Prior unmarked in the area to smash home his and Rocks’ second goal of the game.
Wills threaded a pass through to Nightingale, but the striker was instantly blocked by Reed.
For the Brickies, Dan Palfrey scooped the ball into the box with a low cross but no-one was there to finish.
Prior drove a low shot from long distance which was easily gathered by Reed who got behind the ball well.
But the Rocks’ onslaught became too much for Sittingbourne. On 75 minutes, Prior won a free-kick as a defender failed to clear his lines. And it was the tall striker who curled the ball home powerfully to complete yet another hat-trick.
Substitute Luke Girt got on the end of a through-ball but his cross was headed clear by Stuart Axten.
With ten minutes left it was 4-0. Wills worked hard down the right to chip in a direct cross for Prior, who was in surprising space to power an outstanding header which left Reed standing.
Johnson let fly with a fierce shot from 25 yards but it was somehow deflected away for a corner.
The returning Beck, on from the bench, brought a decent save out of the goalkeeper with a driven shot from distance but again the shot-stopper was equal to it.
But the Rocks were relentless. On 88 minutes Prior totally missed the ball from a pass across the area by Maynard, but then with 90 minutes on the clock, a pass from the other fit-again sub, Ryan, fell to Maynard, who made no mistake with a curling effort, netting the Rocks’ fifth and sending every Rocks fan home happy - and looking forward to Monday.
ROCKS: Stoner, Crane, Whitehead, Wills, Axten, Bond, Royce (Beck 61), Wilkins (Ryan 57), Prior, Nightingale (Maynard 73), Johnson. Unused subs: Turner, Wood
Report by Liam Goodley