Barcham delivered in the nick of time after the lads dominated the final hour of the game only to be denied by a combination of the woodwork and some wasteful finishing.
You could almost hear the collective sigh when Charlie Daniels struck the crossbar 12 minutes from time but with the clock ticking into injury time, Barcham's goal-den moment finally arrived.
It owed a lot to Jacques Maghoma, who picked up possession deep in our half before driving forward, Scott Thyer took over and slipped the perfect pass through to Barcham who sprinted away from the chasing pack and slotted home in style.
It was an impressive performance from the lads with the defence led by the outstanding Charlie Lee, Jamie O'Hara pulling the strings in midfield and Barcham's pace a telling factor as the game wore on.
There was no shortage of bravery either with both Phil Ifil and Leigh Mills playing on for the final 30 minutes after a nasty collision left Mills nursing his knee and Ifil with stud marks up his side.
Forest started brighter in what was always a lively encounter but failed to seriously test Tommy Forecast in the Spurs goal all night - their best chance headed wide by Vincent Fernandez after 28 minutes.
Mills had already crashed a volley onto the underside of the bar by then and Jamie Davis went close again just before the break, Forest keeper Paddy Gamble palming away his effort at full stretch before relying on James Cullingworth to block Daniels' goal-bound follow up.
Daniels was centre of attention as we pushed on for a win in the second half.
The winger should really have done better when Mills nodded back O'Hara's free-kick in front of goal and he then struck the crossbar after Barcham's pace had cut Forest open down the left flank.
Barcham came more and more into the game in the second half - firing a shot just wide, carving out another chance that Thyer couldn't quite get hold of and then failing from 10 yards himself.
Thankfully, he was there again when the late, late chance of glory arrived at his feet - this time he made no mistake and we marched into the fourth round.
GUIDE TO THE ACTION
2mins: Bastians free-kick only half-cleared, Hughes smashed loose ball into Paxton Road.
3mins: Glass burst into the box from Mullarkey's backheel, squared looking for supporting Vickers but Davis nipped in to take ball away.
18mins: WOODWORK. O'Hara whipped in free-kick, Forest failed to deal with it, Mills volley struck the underside of the crossbar and bounced to safety.
22mins: Daniels cross from left flicked off Forest head to Davis at far post, downward header straight at Gamble.
28mins: CHANCE. McGugan free-kick from left found Fernandez six yards out, glanced header wide.
32mins: Deep Davis cross came all the way out to supporting Wright who volleyed high and wide.
35mins: Daniels dribbled between two defenders, early driven cross just ahead of Barcham.
40mins: Dangerman Glass cut inside from right flank, shot deflected but straight at Forecast.
Injury time: CLOSE. Davis quick break from Forest's free-kick, carried ball 50 yards, cut inside last man and shot, Gamble saved at full stretch, Daniels on loose ball and hit the target only for Cullingworth to block.
Half-time: Spurs 0, Forest 0
57mins: Ifil fine tackle in left-back position, saw keeper out of position and went for early shot at near post, didn't quite get it right.
62mins: MISS. Deep free-kick from O'Hara picked out Mills at far post, nodded back for Daniels in front of goal but didn't connect properly header and ball cleared.
65mins: McGugan free-kick from 25 yards bounced awkwardly in front of Forecast, who took ball at second attempt.
67mins: Nasty mid-air clash between Mills and Ifil left both players needing treatment.
71mins: CLOSE. Barcham cut in from left, right-foot shot from 20 yards deflected just wide.
75mins: Barcham pace worked a yard of space, laid ball into Thyer who didn't quite take it under pressure and danger averted.
78mins: WOODWORK. Great work from Barcham down left flank, pace took him into box, cut back from byline to Daniels who swept the ball onto the crossbar from eight yards.
82mins: CHANCE. Lee towering header from O'Hara's corner, ball cannoned through to Barcham, 10 yards out, didn't quite get hold of shot and Gamble saved to his left.
85mins: O'Hara carried ball fully 60 yards, shot from 20 yard deflected over.
86mins: Low cross from Heller after short corner met by Lee but lifted effort into top tier.
87mins: Ifil cool under pressure in box to clear after Pittman failed to connect with header at near post.
Injury-time: GOAL. At last! Maghoma break from Forest possession, carried for 40 yards, Scott Thyer slipped perfect pass into Barcham whose pace took him away from last man before slotting into corner.
Spurs 1, Nottingham Forest 0
Final score: Spurs 1, Nottingham Forest 0
Line-ups: Spurs: Forecast, Ifil, Wright, Maghoma, Mills, Lee, Davis (Heller, 79), Dawkins (Thyer, 58), Barcham, O'Hara, Daniels. Subs: Lewis, Button, Riley.
Nottingham Forest: Gamble, Cullingworth, Blair, McGugan, Fernandez, Hanbury, Glass, Hughes, Mullarkey, Vickers (Pittman, 81), Bastians. Subs: Rigby, Martin, Vickerton, Fairclough.
Andy Barcham's goal in injury time secured a fully-deserved victory against Forest in the third round of the FA Youth Cup at the Lane on Tuesday night.