With the second half in its infancy, goalkeeper Scott O’Rourke booted a long ball over his opposite number Ryan Gosney and fellow former Boatman Mike Spinney got a slight nick to guide it home.
O’Rourke had an outstanding night for the Sydenhams One underdogs, pulling off several decent saves including a penalty stop from Jamie Musselwhite.
“Rourkesy was on fire,” said Brock boss. “Hamble were probably the better side on the night but, saying that, we had five great one-on-one chances.”
Hamble twice had the ball in the back of the net, but both were ruled out for offside.
Holders Christchurch, who beat Brock in last season’s final, breezed past Horndean 4-0 through Dan Crutchley, Harry Cornick, Sam Griffin and Paul Roberts.