Southern Combination leaders Lancing lost their second match in four days on Tuesday evening as Horley Town notched up their eighth straight victory to go second in the Premier Division.
Horley are now five points behind Lancing after the 1-0 win – with two games in hand. Lancing stay top despite this defeat and a 1-3 loss on Saturday at fifth-placed Newhaven.
Before that, Lancing had recorded six league wins on the trot.
Lancing striker Alex Fair hit the Horley post after five minutes but there were few other clear chances in a nonetheless engrossing match.
Horley scored the only goal after nine minutes. Right full-back Scott Robson made a good run from defence, passed to James McElligott, who took the ball deep into Lancing territory before passing for Mario Quissacca to evade a defender and shoot past Mitch Bromage in the Lancing goal.
Horley then played deep, soaking up Lancing pressure and relying on occasional breakaways.
Fair skimmed the bar with a long-range shot for Lancing, Quissacca had a goal disallowed for off-side at the other end, and good work down the right by Lancing's James Beresford and Mitch Hewens ended with George Fenton heading Hewens's cross over the bar.
The second half saw much of the same, with Horley playing increasingly deep and good chances becoming few and far between.
In a nervy last 10 minutes Horley survived a goal-mouth melee and a penalty shout but held on.
Delighted Horley chairman Mark Sale said, "Lancing are a very strong side and our plan was to play deep, and the boys gave a superb disciplined performance. Every man was quality."
Manager Anthony Jupp added, "That's eight wins on the bounce. Unreal togetherness, unreal achievement. There's a long way to go but we are in the mix."