Dan Simmonds’ superb triple strike saw Pagham beat the leaders and and go fourth in the league.
The visitors arrived at Nyetimber Lane clear at the top but that counted for nothing as Pagham were simply brilliant in a win almost no-one could have expected.
The Lions’ unbeaten run stretches back to the middle of October and the Blues did little to suggest they would end it.
Early action centred around free-kicks, with Blues’ skipper Tom Graves going closest for the away side.
Pagham were shooting for fun. Lloyd Rowlatt took advantage of defensive hesitancy to feed Simmonds, only for the shot to go wide.
Andy Chick was masterful in midfield, pinging passes forward to give the Lions strikers much to feed on.
Heath had a good chance when Alfie Rogers picked up a pass from George Hayward. Pagham’s defence held firm.
Great work by new arrival James Thurgar allowed Rowlatt space for a shot but it was just wide of Simon Lehkyj’s post.
A free-kick from Callum Saunders whistled just over the bar.
James Binfield was called into action just before the half-hour, saving well from an Alex Laing shot. A Lions corner gave Callum Overton sight of goal after he collected a Rowlatt pass. The shot went over the bar but the Lions were more up for it.
Heath were rather muted, though, and the Lions kept the visitors at bay, leaving it 0-0 at half-time.
After the break, a superb save from Lehkyj prevented Pagham from taking the lead.
Haywards Heath did try to push forward, Laing being a particular threat, but it was the Lions who ran the show.
Simmonds and Overton were looking like scoring at every opportunity and it was a surprise that the first goal didn’t come until the 70th minute.
It was well worth the wait, though, Simmonds’ scything run cutting through the Blues’ backline before striking a superb solo effort beyond Lehkyj.
An awful decision by the officials could have handed Heath the equaliser on 74 minutes as they were awarded a free-kick controversially. But a poor free-kick saw justice done for the Lions.
Bailie Rogers became the first player to leave the field, a challenge ending his involvement. On came Joel Daly.
James Thurgar could have got his second in two games with a header that went close.
Simmonds’ second followed a left-sided attack which gave him time to shoot past Lehkyj. With just under five minutes left of normal time, Pagham made sure of the points.
Overton went on a run which could have seen him score before Simmonds wrapped up his hat-trick. Rowlatt’s ball in gave Simmonds a gilt-edged opportunity and Lehkyj no chance.
Pagham: Binfield, Wiggans, Cox, Davidson, Booker, Horncastle, Rowlatt, Chick, Simmonds (Crouch 89), Overton, Thurgar. Subs: Wollers, Bingham, Ashmore