Peterborough meanwhile, didn't include new signing Steve Jenkins as he had "flu". Yeah right Steve, I'll bet you'll be right as rain for Saturday. While they also included danger-man Andy Clarke and Sagi Burton on the bench.
Notts, who attacked the goal their supporters were behind for the first half, were immediatly under-pressure as Mildenhall was forced into a sharp stop at his near post from a Richard Logan strike.
We then found our feet a bit, gaining 5 corners in the opening few minutes, one of which nearly produced an own-goal.
But with 10 minutes gone, it was from one of these Notts corners that produced Peterborough's opener.
Simon Baldry was caught dallying on the ball in the centre circle after Caskey's corner was cleared and David Farrell raced down the left-wing before cutting it back to Curtis Woodhouse who expertly slotted in the bottom corner, beyond Mildenhall.
It took 5 minutes before The Magpies hit back, with Mark Stallard's curling shot from the left deflected over by Simon Rea.
Notts could then count themselves lucky that they weren't two down, as Ian Richardson brilliantly cleared Curtis Woodhouse's shot off the line.
With 25 minutes on the clock, Mildenhall was required to make a smart stop from ex Notts man Andy Legg's rasping long range effort. Legg had an absoloute blinder playing in the centre of midfield for the home side and how Notts must wish they could have 'Leggy' back now.
On 27 minutes, Peterborough put themselves two goals to the good. Curtis Woodhouse, who along with Farrell was the best players on the pitch, played Richard Logan through and Logan cooly tucked it past Mildenhall at his near post.
Darren Caskey, who refused to put any work-rate in throughout the game, then found himself in hot water as he put in a very late tackle on Curtis Woodhouse, injuring the Boro' man in the process.
As Posh fans bayed for him to be sent-off, while also commenting on Darren's weight, the referee opted sensibly to give him a yellow.
Peterborough should have been 3 up on 38 minutes when, when clean through Callum Willock slid the ball wide of the post with Mildenhall beaten.
Just before half-time though and Notts somehow managed to get themselves back in the game. Simon Baldry cross from the right was mis-hit, but it looped high in the air, Mark Tyler flapped and Paul Riley was on hand to smash the ball into the net.
The Magpies went in at half-time 2-1 down, when it could have easily been 6 or 7.
HALF TIME: Peterborough United 2-1 Notts County
Incredibly, just after half-time and Notts were level.
The game was certainly not lacking in entertainment, as David Farrell volleyed over the ball when well placed to put his team back in front.
But on 55 minutes, Peterborough were back in front. Darren Caskey decided to head the ball back to the opposition, and Willock played in Farrell who expertly volleyed the ball home.
With an hour on the clock, Dearden decided to make the change that Notts' fans had been hoping for, bringing on young Shaun Harrad for the tremendously ineffective Tony Hackworth.
Harrad almost had an immediate impact, but he blazed his shot well over the bar.
Ian Richardson was then somewhat bizzarely booked for a 'foul' on Curtis Woodhouse, even though the Notts skipper clearly got the ball. This was typical of the referee, who angered both sets of supporters throughout the game.
Billy then made his second change, bringing on Michael Brough for Paul Bolland, who worked hard but looked like a bit of a headless chicken most of the time.
Peterborough 'keeper Mark Tyler then produced an outstanding save to keep out Stallard's header, as The Magpies looked for that elusive equaliser.
Shaun Harrad brilliantly turned Sagi Burton, his shot was well saved by Tyler, but somehow Mark Stallard managed to put the rebound wide when faced with an open goal from 6 yards out.
The miss would prove costly as Posh then put the game beyond doubt. Boro' were awarded a dodgy free-kick for a supposed foul by Kevin Nicholson and the ball was headed back in from the back post, which left Richard Logan with the simple task of slotting the ball into the empty net.
Four minutes later and it was embarrising. A disasterous error by Nicky Fenton, who looked about as happy playing at right back as Caskey does when told he's told that Greggs have sold out of Pies, let in substitute Andy Clarke who made no mistake to slot the ball past Mildenhall to make it 5.
In the last few minutes, 16 year old Chris Rhodes was given his debut, replacing one of Notts' better players, Simon Baldry, while Posh came close to making it 6 and one of their players was booked for a kick at Shaun Harrad when he could have easily been sent-off.
FULL TIME: Peterborough Utd 5-2 Notts County
A diabolical performance from Notts, which has now turned out to be Dearden's last in charge. The fact Billy decided to tell the players BEFORE the game that he was leaving can't have helped. Only Riley, Baldry & Harrad can come out of this game with their heads held high, while Hackworth & Caskey should be ashamed of their lack of effort throughout the game.
The new manager will have a hell of a job on his hands.
Match ratings to follow.