The Cobblers inflicted revenge on Barnet in the cruellest fashion possible by ending their stay in the Football League.
Northampton ran out 2-0 winners in front of the third largest Sixfields crowd and the biggest for more than 15 years.
And results at the top end of npower League Two mean Town will play Cheltenham in the play-off semi-finals, with the first leg taking place at Sixfields on Thursday night.
Roy O’Donovan scored his second goal in as many games and Luke Guttridge completed the victory that helps banish some of the memories of the 4-0 rout at Underhill in October.
Barnet attacked only sporadically and were found wanting in attack for long periods, while the Cobblers were the better side throughout and ended a five-game winless streak with a crucial, momentum-providing victory.
Ben Harding had a good start to the game and found Jake Robinson with a dead-weight pass of which Davids in his prime would have been proud.
Robinson’s first touch and powers of acceleration took him beyond the defence but his shot lacked power and Graham Stack turned it away for a corner.
Mark Byrne fired a shot into the side-netting from Luke Gambin’s low pass from the left wing in what was a wide-open start to the match.
Roy O’Donovan failed to make a good contact on a Luke Guttridge pass from 14 yards, Stack easily collecting his left-footed attempt.
Barnet got the second half off to a lively start, Elliot Johnson hitting the crossbar with a cross and Ben Tozer clearing Jake Hyde’s follow-up off the line.
They continued to make the running as it progressed too, Luke Gambin twice finding space down the left and worrying Lee Nicholls with his second ball in.
But they had few shooting opportunities, and when one came the way of O’Donovan, he showed a cool head and perfect technique to score it.
Guttridge played a good pass into him but he still had some work to do to convert it.
Minutes later, Guttridge scored the result-sealing second, collecting Adebayo Akinfenwa’s lay-off and rifling across Graham Stack and into the corner.
It sank Barnet, both in the league table and on the pitch and their response to the goals against was almost non-existent.
Instead they played out time in the manner of a side who were more concerned with not conceding any more goals than preserving their Football League status.
Cobblers: Nicholls, Tozer, Cameron, Carlisle, Collins, Robinson, Hornby, Harding, Guttridge, O’Donovan, Moyo
Subs: Akinfenwa (for Moyo 56), Dias (for Guttridge 76)
Not used: Johnson, Hackett, Snedker, Wilson, Moult, Dias
Barnet: Stack, Yiadom, Stephens, Flanagan, Johnson, Marsh-Brown, Davids, Weston, Byrne, Gambin, Hyde
Subs: Nurse (for Marsh-Brown 72), Crawford (Byrne 76), Vose (for Hyde 87)
Not used: Fuller, Kamdjo, Oster, Kuipers
Away fans: 1,360