Michael Jacobs' double put the seal on 10-man Northampton's hard-fought 3-0 victory at AFC Wimbledon.
Adebayo Akinfenwa's spot-kick opened the scoring and, although midfielder Nick McKoy was dismissed on the stroke of half-time, Jacobs' two long-range efforts secured victory.
The Dons threatened early but Northampton struck first when Marlon Jackson broke free and the Bristol City loanee was hauled down inside the area on 17 minutes by keeper Seb Brown.
Akinfenwa calmly rolled in the penalty to net his fourth of the season, and his bullet header would have doubled the scores if it were not for Brown's sharp reflexes, while Jackson's effort rattled the crossbar.
The Cobblers' cause was not helped when McKoy saw red for lunging at Sammy Moore, but Wimbledon offered little in response apart from Luke Moore's dangerous cross which fizzed across goal.
Brown denied Jacobs on the counter once, but the winger's 71st minute 30-yarder crept through his legs and a stinging drive six minutes later capped a dismal day for the Dons keeper.
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