Crawley Down Gatwick went a long way towards cementing the runners-up berth with three further points against their nearest rivals, Storrington.
Stout defensive work allied to rather erratic Anvil finishing kept the game tight until the final minutes.
Down went close to taking the lead when Sonny Barton struck a corner that had a James Day header rattling the upright.
The game then swung the Swans’ way with a Sam Elliott free-kick from the halfway line testing Andy Greaves in the Anvil goal.
Down took the lead on 14 minutes when a corner by Myles Pitt caused confusion in the Swans defence before finding Sam Cane who made no mistake.
This settled the home side down and from then on they started to dictate the game with some neat passing.
Cane struck the upright and Day again using his height to nod over, but that missing ingredient of a second goal continued to be a problem, with next being midfielder Lee Thomas also heading over.
Storrington’s Elliott entered the book for colourful language which did not go down well with the home crowd after an incident outside the box.
A Cane shot being hacked away, as the Anvils continued to chip away at the Swans’ backline.
On 67 minues manager Paul Cooper took off Ben Brooker who had looked lively all game and replaced by Oli Leslie who at once danced his way through the Swans’ defence to free up Thomas who in turned fired over, midfielder Thomas an unsung hero who always gives off his best, but tends to get overlooked.
For the Swans it was a case of containment as they continued to offer little upfront, and mainly relied on free-kicks and the odd corner to get them out of trouble, though on 80 minutes when Culley then nearly bucked the trend with a rare break and shot that had Greaves scurrying across his goal.
Further changes on the Anvil bench saw Josh Brown replace Pitt to try for this second goal, as anxiety from the field started to reach the terraces, as chances were still being created, but couldn’t be converted.
Then came that bit of magic which managers are paid for, that final substitution on 85 minutes when newcomer Tom Gannon entered the fray, replacing Cane.
Within minutes he became the hero of the hour when thumping home that vital second goal.
There was relief all-round as Gannon’s fairlytale goal brought joy as the Down faithful realised second-placed they had gone eight points clear of their nearest rivals.
Crawley Down Gatwick: Greaves, Cooney, Barton, Spence, Dixon, Day, Greig, Thomas, Brooker (Leslie), Cane (Gannon), Pitt (Brown)
Unused sub: Walsh
Man of the Match: