This was the climax of an astonishing 11-game revival which against all the odds has carried Notts County to Second Division safety.
The big Australian has scored 11 times in 11 matches and was at it again with the first vital goal against below-strength Huddersfield Town.
Allsopp's flying header gave Town goalkeeper Martyn Margetson no chance but much of the credit belonged to the skillful build-up of midfielders Darren Caskey and Richard Liburd.
Town's best chance of an equaliser fell just before half-time when Delroy Facey should have done better than to blaze wide from an angle.
Town's probings meant that Notts could not sit back on a one goal lead and they nearly snatched a second in the early moments of the second half. Defender Nick Fenton's header from a corner was scrambled on to the post and then for a corner.
It was at this stage of the match when the Jimmy Sirrell stand did a mexican wave of "Stand up if you're staying up" and it looked pure quality from the view of the Derek Pavis Stand.
Stallard was never really presented with a chance and indeed it was Town's turn to find the back of the net.
Notts substitute Paul Bolland needlessly pushed Facey over in the box and from the penalty spot Kenny Irons easily beat Stuart Garden for the first visiting goal at Meadow Lane in five successive wins.
When the whistle blew, thousands of black and white fans flooded the pitch of Meadow Lane, picking up their heroes like Danny Allsopp and clutching at the likes of Fan favourite Stuart Garden. It was a marvellous sight and they stayed their for many minutes applauding the team when they came out onto the balcony to give their thanks.
Notts manager Bill Dearden afterwards congratulated his backroom staff and players and said the credit belonged to them. Dearden also congratulated his former club Mansfield Town on achieving promotion.
So onto another season then, and remember: The future's bright, the futures Black and White!