United had a couple of early half chances but it wasn’t long before the visitors forced themselves upon the game.
It took only four minutes for Haddington to get their noses in front when a free-kick was met at the back post by Simpson who out muscled his markers and headed into the corner.
To their credit United managed to rally as they tried to get back into the game.
Dylan Honeyman whipped a dangerous cross into the box which visiting ‘keeper Cornet managed to nudge to safety.
United stayed on the front foot but found Cornet a tough obstacle to pass.
The visitors managed to get their noses even further in front shortly after the half hour mark when another set piece was met by Watson this time and he again nodded into the Saints goal.
The goal seemed to knock the stuffing out of United and they alarmingly fell completely out of the game.
Just two minutes after losing the second goal it was 3-0 when King picked out the top corner of the United net from 35 yards.
The damage was done before the break when the ruthless visitors added a fourth goal.
There was an element of misfortune about the goal when a hopeful chip forward bounced badly for the Saints defence and allowed Simpson to break through on goal and net.
Rather than United eating into the advantage, it seemed a matter of time before Haddington made it 5-0 as they started the second half brightly.
But with half an hour to go they took their foot off the pedal.
Saints managed to take advantage and had their best spell of the game with the points already lost.
Blaney got one back when he volleyed a terrific effort into the Haddington net.
St Andrews United: Curtis, Fital (D Fleming 60), Macaulay, M Fleming, Doig, Blaney, Honeyman, Penman, Andrew,Quinn (R Cunningham 63), Rendall (King46).
Subs: C Fleming, Stark.