WGC Res lost their third away game in a week to a 95th minute goal, when the home side's centre-half scored his second thunderous free-kick to claim the points.
In difficult conditions, played in very windy weather, WGC Res went 1-0 up after a goalless first-half when Dan Harper's free-kick was excellent saved, only for the ball to come free and Nathan Studholme was able to tap it home.
WGC Res held this advantage until three minutes from time, when the St Margaretsbury Res central defender crashed in his first goal and sadly, for the Citizens' second string , repeated the feat deep into stoppage time.
Said Res co-manager Russ Giblin: "We are absolutely gutted to be leaving with nothing. It was another very good performance and the longer the side play together, some of the easy mistakes we are making, can be ironed out.''
Harpenden Tn Res 2, Welwyn GC Res 3
WGC Res picked up their first points under the new management of Sav Caliskan and Russ Giblin, when they travelled to Harpenden Res on Thursday night.
Player-manager Caliskan scored twice in his side's victory, netting early from a mishit cross and then doubling the tally with a header at the end of a well worked move.
But Harpenden Res were back in the game before half-time when they scored with a well executed lob over keeper and skipper Freddie Hester.
A rousing half-time team talk had its effect with a WGC Res third scored by Craig Arnott and although Harpenden Res pulled back a second goal just before the end, it couldn't alter the destination of the points.
There were outstanding performances from Stefan Saywell, the returning Jake Hoy and player-manager Caliskan.