Walsham won 3-0 to record a very impressive seventh successive victory and move within two points of their opponents.
Next up for Paul Smith’s side are Wisbech Town, who dropped to third place after being held 3-3 by Kirkley & Pakefield.
Scott Johnson scored a late equaliser for the home side.
Dereham Town are now third after beating CRC 4-0 and have three games in hand on both the sides above them.
Next up for the Magpies is a visit to Ely City, whose FA Vase victory on Saturday increased their winning sequence to six games.
Dereham Town are obliged to play Norwich City two days beforehand in a replayed Norfolk Senior Cup tie.
Wivenhoe Town ended a run of nine successive defeats with a welcome three points against relegation rivals Diss Town.
Wivenhoe had conceded twenty-one goals in their previous three games but came out on top by 3-0 on Saturday.