It was a quiet opening to proceedings at a rainy Meadowbank Stadium, the Bees first chance fell to JJ Hooper, but his effort was comfortably dealt with by Sam Howes.
Up the other end, Harry Taylor had to be alert to get a crucial touch on a dangerous cross with Jason Prior lurking behind him six yards from goal.
It would be the National League South side who would take the lead after a cross was headed against the crossbar by Prior, before James McShane scored on the follow-up. It was almost two just minutes later as the ball struck the post after a dangerous ball flashed across our six-yard box.
Tim Flowers side soon found their feet and almost levelled through Hooper after he headed onto the roof of the net following a good delivery from Jack Connors.
Ten minutes before the break, we were level as a neat move found debutant Ben Fox on the edge of the box, he made no mistake as he curled home.
The hosts responded almost immediately, as a quick free-kick was played wide before Prior powered a header home from a brilliant cross into the Bees box.
The first chance of the second half fell to substitute Alex McQueen, he flashed an effort just wide of the post following an extended spell of Bees pressure.
Up the other end, Loach was called into action as he tipped a low Matthew Briggs stop behind for a corner.
With twenty minutes left on the clock, we were down to ten men as Fox's debut ended early as he was shown a straight red card for a late tackle. Fox was already on a booking but it didn't appear that the ref showed a second booking.
As the game ticked on, the 10-man Bees continued to force the issue, with second half sub Josh Walker having a golden chance after being found by McQueen, but our number 22 couldn't make a clean connection to guide it goalwards.
As the match went into five added minutes, the hosts sealed the victory as Luke Moore stepped up to convert a penalty, after Loach had brought down a Dorking attacker.
It wasn't the start new boss Tim Flowers wanted and leaves him plenty to ponder heading into the busy Christmas period.
Barnet: Loach, Pascal (McQueen '45), Connors (Faal 86'), Dunne (c), Hooper (Walker 70'), Effiong, Taylor, Fox, Binnom-Williams, Mason-Clark, Nugent.