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Dover slipped to their first defeat in five National League matches before the TV cameras at Barnet on Saturday.
A win in the lunchtime kick-off would have taken Whites out of the bottom four ahead ahead of the afternoon programme, but they fell behind when Jack Taylor struck 11 minutes into the second half.
Top scorer Inih Effiong squandered the best chance to equalise when he shot high and wide when clean through and Barnet sub Mauro Vilhete then doubled the home lead in time added on.
Whites made just one change to the side which had beaten Fylde in their last league game with the recently re-signed Ricky Modeste coming in for the injured Jai Reason. Defender Scott Doe, another recent acquisition, was named on the bench.
Barnet had lost their previous three home league games but made the brighter start with Wesley Fonguk seeing his low drive deflected wide after 11 minutes.
Dan Sweeney glanced a header wide from a corner and Cheye Alexander had a free-kick in a good position blocked by the wall but otherwise Barnet were unable to really test Whites keeper Mitch Walker.
Gradually Dover began to grow into the game and before half-time it was the visitors who created all the best chances.
Their first real sight of goal came on 25 minutes when Stuart Lewis saw his fierce rising drive deflected over for a corner and two minutes later the Whites midfielder forced home keeper Mark Cousins to parry well low away to his right.
Anthony Jeffrey then forced Cousins into a low save at his near post after cutting onto his right foot as the home fan's frustration began to mount.
Dover's best chance of he first half came on 35 minutes when Jeffrey's near post cross fell to top scorer Effiong who spun well only to volley over.
Effiong went close again four minutes before half-time when he diverted Jeffrey's hard hit cross goalwards but the ball was hacked clear.
There were a few boos from the Barnet faithful as the players left the pitch at half-time and boss John Still made a change during the break replacing striker Immanuelson Duku with Byron Harrison.
The home side immediately looked reinvigorated and might have broken the deadlock in the 50th minute when Ephron Mason-Clark rounded Walker only to thump his shot against the upright.
Barnet gained encouragement from that and within six minutes they were ahead.
Taylor produced an accomplished first-time finish from 12 yards after home skipper Callum Reynolds had picked him out with a deep angled pass from halfway.
Whites promptly replaced Jamie Allen with Alfie Pavey but they nearly fell further behind on the hour when Mason-Clark hit a rising shot that arrowed just wide of the far post.
The visitors should have drawn level in the 64th minute when Effiong robbed Elliott Johnson, but with only Cousins to beat he fired horribly high and wide.
Lewis then forced Cousins into a save from Pavey's knockdown and, as the game opened up, Barnet went close twice in a matter of seconds.
First Walker beat away Vilhete's close-range effort before Harrison saw his shot deflected wide.
Walker was called into action again on 74 minutes when he tipped over Vilhete's header and as Barnet sought a second goal that would have killed the game off Medy Elito curled a shot against the crossbar with Walker beaten.
Whites tried to stage a late rally but too often their delivery into the box was not good enough and in the 91st minute Vilhete raced clear before burying a shot into the bottom corner.
There was still time for Walker to produce a flying save to deny Taylor his second.
Dover: Walker, Passley, Brundle, Lokko, Taylor, Gomis (Doe 74mins), Lewis, Modeste, Jeffrey (Nortey 74mins), Effiong, Allen (Pavey 58mins); Subs Worgan, Diarra.
Barnet: Cousins, Alexander, Johnson, Reynolds, Adams, Taylor, Fonguk, Elito, Sweeney, Mason-Clark (Vilhete 68mins), Duku (Harrison 46mins) Subs: Matrevics,Coulthirst, Bettamer.
Attendance: 1011