The Dons travelled to Walton in search of a point to secure the title, but instead Walton & Hersham stamped their authority on the other promotion spot with an emphatic and richly deserved victory.
The only change to the side that clinched promotion came in midfield, as Chris Gell started in place of Micky Woolner, who was judged fit enough for a place on the bench.
But Walton & Hersham, in search of three points to cement themselves in the other automatic promotion spot, started strongly. Harkness sent a low shot narrowly wide and his strike partner Nwokeji fluffed an effort from the edge of the area when free.
Wimbledon gradually grew stronger and Howard shot wide from a free-kick after a Steve Butler header was blocked. Walton continued to threaten and the game ebbed and flowed from end to end.
A terrible Smeltz backpass put Steve Butler under pressure and the Dons were forced to concede a corner midway through the first half. It was swung in to the near post and a pair of Walton players bundled it past Paul Smith, with the PA announcer giving the goal to Frontin.
The home side continued to have the better of it, and sent two further chances wide as they dominated with the advantage of the wind. Richard Butler did his best to get the Dons going, pulling a long ball from Howard back across the face of goal. It was hacked behind for Wimbledon?s first corner as Farr threatened. But the cross was cleared.
Matters turned worse for the Dons as half-time approached. Harkness trapped a cross-cum-shot on the edge of the six-yard box and swivelled to loop a shot past Smith and in off the far post for a 2-0 Walton lead. It stayed that way until the interval, which must have made for an interesting half-time chat from Dave, JT and Warren.
The management team switched things around for the second half, with Sonny Farr taken off and replaced by Joe Vines. Vines slotted into a back three with Howard and Cooper. Steve Butler was pushed into midfield and the Dons committed men forward in search of goals.
But the first chance of the second period fell to Walton, as ex-Don Wes Goggin somehow failed to provide the final touch on the edge of the six-yard box with the goal at his mercy.
The Dons enjoyed greater possession than in the first half, but chances proved hard to come by. Gindre came out well to claim a few crosses, but was otherwise untroubled. The first shot of any note came from McDowall on 69 minutes, but he curled it straight at the keeper.
Almost immediately the home side made it 3-0. Nwokeji tumbled on the edge of the area under a challenge from Joe Vines and Riddell stepped up to fire an excellent free-kick into the top left corner of the net.
After that, in truth only one side really looked like scoring, and they were wearing red and white. With 12 minutes remaining Harkness nodded home from a corner for a 4-0 lead as a defeat became more of a rout.
For all that Walton were impressive, there?s no hiding the fact that this was a poor Dons performance. But to put it in some kind of context, it was only the third league defeat of the season and, if you?re going to fail to wrap up the title at the home of your nearest rivals, you might as well do it in style.