The Rebels will be left ruing a number of missed chances, not least in the very first minute when a defensive mix-up from the visitors let in Lee Riddell, but he mishit his shot and Justin Gray in the Farnborough goal was able to recover with Davies lurking.
Slough continued to threaten, with Davies volleying well wide from a Harper knock-down, but Farnborough settled into the game and began to dominate, creating a number of chances. A left-footed effort rebounded back off the post and was cleared away, whilst Byron Bubb blazed one effort over the bar, and Darren Wheeler forced a good save low down from Barnard.
Farnborough were all over Slough, but the hosts took the lead against the run of play. A well-worked move saw Dave Thomas break through the middle, before giving the ball to John Gray on the left wing. Gray's beautiful cross was tucked away by Terry Davies on the volley at the far post.
Minutes later, Slough came so close to doubling their lead as Laurence Brown's right wing cross was volleyed just over the bar by Dave Barratt.
Predictably Farnborough pressed forward in search of a goal, and were rewarded with the equaliser on 32 minutes. A shot from Bubb came back off the post and was tucked away by Rob Saunders, sliding in to improve further his tremendous strike-rate from midfield this season.
Slough were forced back for the rest of the half, and only good covering tackles prevented Wheeler from scoring, with the winger eventually putting his shot wide under pressure from Harper and Daly.
Just before half-time Slough had a chance to re-take the lead, but Terry Davies' shot after cutting inside was held well by Gray.
A downpour during the half-time break made conditions even more difficult in the second half, and it seemed as though Slough adapted better to the conditions initially at least, taking the lead for a second time in the 49th minute. Gray won a corner out on the left, from which Terry Davies powered a header all the way through from the edge of the box. The ball somehow found its way into the back of the net with Barratt swinging but unable to get contact on the ball, and so Davies was credited with his 10th goal of the season.
Davies found himself with two golden chances to score during the second half, but was thwarted on both occasions by Gray.
Slough were made to pay for these missed opportunities in the 63rd minute with a Farnborough equaliser. Lee Riddell conceded a free kick on the corner of the penalty area, and an unmarked Adam Doyle powered in a header from Saunders' cross to level things up.
Davies was in the thick of the action yet again, forcing a good save from Gray, with the ball agonisingly eluding Abby Nsubuga at the far post, on as a replacement for Barratt.
However the final twenty minutes or so consisted mostly of heavy Farnborough pressure, with Slough forced into some desperate, sometimes heroic, defending.
Richard Barnard produced a wonderful save from a looping Saunders header, stretching to tip the ball just over the crossbar. More chances arrived as Barima's cross seemed to get stuck in the mud, eluding Farnborough strikers in attendance before being hacked away. Dean Harper produced one magnificent clearance off the line after a combination of Daly and Riddell had blocked yet another effort.
With Slough visibly tiring and forced to replace both Davies and Barratt, who had run themselves into the ground, Farnborough kept piling forwards and got their reward with a goal one minute into injury time. After an initial shot from Saunders was saved brilliantly low down by Barnard, this time Slough's luck ran out as Barima was on hand to tuck the rebound away into an empty net to leave Rebels supporters and players devastated after what was a terrific effort and a great advert for the South & West division.
Farnborough Line up
Gray, Hill, Oliver, Doyle, Evans, Rumbold (c), Saunders, Ciardini, Bartley, Bubb, Wheeler. Substitutes: Barima, Pestle, Richardson, Beazley (gk).