Sutton's academy side progressed to the second round of the FA Youth Cup after a thrilling penalty shoot out victory over Colchester, who play one level higher than U's in the Professional Development League.
Sutton, who had a number of Under 16 squad members in the team, had an unsettling start when goalkeeper Sam Roberts limped off inside the first ten minutes to be replaced by Lenny Jones, but went ahead when Joden Trickett outwitted two Colchester defenders before cutting in from the right and scoring with a low left footed shot.
There was almost a second when Cameron Sullivan's inswinging corner was clawed out by goalkeeper Harrison Chamberlain, but Colchester cleared downfield and Burak Sabah raced away from Vinnie Tume to cross low for Jamie Arnold to equalise.
Sabak was involved again early in the second half as Colchester went in front, his right wing corner ending up in the net with a possible deflection off Tume, but Sutton fought back to level on the hour when Liam Moore's 25-yard free kick went through Chamberlain's hands in to the net.
Both sides could have won in normal time or the extra half hour, with Jones making two good stops with his legs and Khyan Edwards lifting the ball over the bar after he had sprinted clear from the halfway line early in the second period of extra time, and over 120 minutes a draw was about the right outcome, Colchester's marginal advantage in possession and territory matched by U's resilience.
The penalty shoot out was of a very high quality, with fifteen penalties impressively converted before Colchester defender Elkanah Akor's effort was saved by Jones to his right to send U's through to the second round.
Sutton: S Roberts(sub L Jones), V Tume(sub J Marquis), C Sullivan, L Moore, D Urpens, J Eccleston, K Edwards, B Lambourne, J Trickett, J Fennelow(sub C Grant), G Vorster.