Horsham slipped to their ninth league defeat of the season despite a battling display at championship-chasing Hampton and Richmond Borough.
The Hornets had the better of the first half with the Beavers' keeper Adrian Blake tipping over a long-range effort from Rob Hughes after five minutes and pushing away a Carlo Castrechino shot two minutes later.
Horsham had a strong penalty claim when John Timlin was pulled back as he burst into the penalty area on the stroke of half-time before Sam Okafor cleared a shot off the line with the Horsham players still protesting.
Horsham's stand-in goalkeeper Luke Barton made his first real save of the game on 65 minutes when he produced a sharp block from Adrian Allen but he had no chance when the ball fell to Allen four minutes later and he chipped in.
Manager John Maggs said: "When you are at the top you get results like that.
"We put in a big performance and didn't deserve to lose. We're sick of losing but if we put in performances like that we will pick up points."
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