Some outstanding defence, led by unforgiving skipper Kevin Wilson, kept the visitors to a 5-0 lead at half-time.
For the second half, Alton re-united the former 1st XV duo of Tony Hopkin and Bruce Oliphant in the second row, while Matt Curtis added pace and aggression on the wing.
The forwards drove for the Farnham line, but Hopkin was held up and although Matt Chapman followed in to dot down, the try was ruled out for a forward pass. The chance was gone and L’Escargot clung on their lead.
Alton U14s, meanwhile, have made a winning start to their defence of the Hampshire title and are through to the cup quarter-finals. On Sunday, the U14s beat Trojans 50-17 in a friendly match at Anstey Park.