United reserves finally ran out of steam as they succumbed to a late onslaught from league leaders Mortimer
Jordan Harry reacts to a cross with Theo Alexander and Will Edwards looking on.
It all looked so different on 59 minutes as late call up and assistant first team manager Yash Romeo stabbed home his and United's second goal giving the visitors a shock two goal lead over undefeated Mortimer.
Played in what was often torrential rain it was Marlow who began the game strongly, taking the game to their opponents playing at times some excellent football on Mortimer's exspansive pitch.
They took the lead midway through the half as Lewis Drapers free kick from the left of the area was parried by the keeper, the ball going over the line off Romeo's knee.
Both teams attempted to keep the ball on the floor and it was Mortimer's midfield that were forcing the visitors on the back foot as the half progressed, the pressure seeing the ball hitting the Marlow bar before being cleared off the line.
United hit back on the break , Conner Hoyte causing a deal of problems down the left, with Romeo three times coming close, twice with headers and once with a stinging shot.
The half closed with United well worth their half time lead.
The pace of the game continued after the break with Marlow again looking the more dangerous in attack.
They had bought on their only sub Delroy Howell at half time and he was soon in the thick of the action and it was the sub who eventually provided the cross from United's right for Romeo to convert from close range.
Mortimer , with a full compliment of subs began to add fresh legs to the proceedings and 5 minutes after United's second they pulled back a goal as a free kick was punched onto the underside of the bar by keeper Baldwin with the ball crossing the line.
Goals change games and with Marlow beginning to look leg weary Mortimer took full advantage and soon after a defensive slip allowed a Mortimer forward a free run on goal to take the lead.
Once ahead the floodgates opened with the hosts pouring through the now large gaps in the United midfield and defence. Three goals were fired home in quick succession .
Marlow kept plugging away, Howell missing a decent chance to reduce the arrears but eventually they were pleased to hear the final whistle as the rain continued to fall.
Mortimer showed why they are heading the table, being clinical in there finishing having been second best for much of the game but Marlow can take heart from a gutsy performance, and who knows with a full bench things may have been different.
Train with the Best - Win a training session with the England 6-a-side squad
Team selection has not been published for this fixture yet.