Cambridge had worked hard to win the ball and closed the Terriers down effectively during a dull first half in which Irons' deflected shot and Schofield's drive stright at Lionel Perez stood out.
Paul Wanless had his effort blocked by Nathan Clarke in a first period that saw neither 'keeper over-employed.
The reason for this was clearly down to the commitment and work-rate of the Abbey Men which made Town look very ordinary in comparison.
The narrow pitch on the Abbey Stadium meant that Schofield and Thorrington had little room in which to play but the Terriers kept plugging away - Schofield got in an early shot in the second half.
Alex Tudor led a flurry of Cambridge chances which were stopped by Martyn Margetson with some help from Nathan Clarke.
Changes were needed and Lou Macari opted to replace a flagging Delroy Facey with Clyde Wijnhard who immediately put himself about and offered a different option up front.
Cambridge were shaken and tried to adapt but Wijnhard proved too tough to contain.
Knight scored his 7th goal in 6 games when he ghosted into the area and met Clyde Wijnhard's cross with a solid header which flew into the back of the net.
Wijnhard had only been on the pitch as a substitute for a few seconds and his first touch of the ball was won after he chased down a lost cause and dug the ball out inches from the goal line to produce the cross which Knight met with his head and finished with aplomb.
The goal had been scored but the job was not over as Cambridge re-doubled their efforts and pressurised Town into a tense finale.
The Terriers were defending deep once again and paid the ultimate price just over a minute from time when Gareth Evans was adjudged to have held Paul Wanless in the area.
Wanless fell under the clumsy challenge and the referee did not hesitate to award the penalty.
Town fans were up in arms at the injustice but there was relief a minute later when Ian Ashbee stepped up and fired a very poor, weak penalty well wide of Margetson's goal.
The Welshman had guessed right anyway but the miss ensured that Town took away all three points from the Abbey Stadium.
Read Doug Thomson's match report in the Examiner on Monday. Have your say in the messageboard below. Selected comments will be published in the Examiner.
Cambridge (4-4-2): Perez, Ashbee, Duncan, Wanless, Youngs, Gutteridge, Tudor, Tann, Jackman, Goodhind, Murray
Subs not used: Marshall, Fleming, Sculley, Revell, Bridges
Goal Attempt: Ashbee missed pen 90
Town (4-4-2): Margetson, Jenkins, Clarke, Evans, Gray, Thorrington, Schofield, Holland, Irons, Facey, Knight
Subs not used: P. Senior, Moses, Heary, Hay, Wijnhard
Scorer: Knight 65
Referee: Steve Tomlin (Lewes)
Attendance: 3,728 (893 Away)
Match points follow on subsequent pages.
93 mins: David Bridges came on in a last throw of the dice for Cambridge.
92 mins: Gareth Evans was hauled off as Thomas Heary came on.
91 mins: Thomas Heary was coming on as Town decided to stabilise and protect their lead.
91 mins: Irons struck a late free kick inches over the bar from a similar position top the Wycombe goal.
90 mins: Town had 5 minutes to preserve their lead in injury time.
90 mins: Ian Ashbee hit the ball wide!!!!!!!
89 mins: Gareth Evans was penalised for holding a Cambridge player in the area - he went down like he was pole-axed - the referee blew immediately for a penalty!
87 mins: Ashbee fired a rising shot over the bar. Margetson bellowed at his defenders to push up. Thomas Heary was preparing to come on.
86 mins: Knight was slow to react when a chance of the ball coming free came up.
85 mins: Town were sitting dangerously deep as the home crowd bayed their team on.
83 mins: Knight was foiled upon coming up for the ball.
82 mins: Cambridge were piling men forward with a direct game to chance their arm for a goal.
81 mins: Irons blocked a Cambridge attack and set Holland free - Jenkins was flagged offside though.
80 mins: Hay, on as a sub, fired in a shot which eventually fell to Knight but he fired wide.
77 mins: Knight's shot and turn was wide.
74 mins: Wanless' cross was parried by Margetson and cleared by Clarke with a header as they continued to push for an equaliser.
72 mins: Wijnhard flicked the ball into the path of Thorrington.
67 mins: Murray's long distance shot was wide.
65 mins: Wijnhard's first touch was a cross which took the ball into Knight's path. The little striker couldn't miss with a free header!
64 mins: Delroy Facey was swapped for Clyde Wijnhard as Lou Macari decided to freshen up the Town attack.
63 mins: Margetson rose to the challenge and collected the ball from a Cambridge attack despite being fouled.
61 mins: Margetson watched a Jackman strike fly wide after Jenkins had helped to clear the ball from the corner.
60 mins: Town went to sleep and Tudor almost pulled off a stunning goal but for intervention from Margetson.
59 mins: Knight won the ball off Tann but he couldn't find Kenny Irons on the edge of the Abbeymen's area.
57 mins: Clarke producing a diving header to clear the ball after Cambridge pressure had put them within shooting range.
53 mins: Schofield's dribble took him into range and his shot was initially dropped by Perez but the Frenchman picked it up when it became clear that there were no Town players closing in for the rebound.
52 mins: A skillful run and floated cross from Thorrington was looped just wide of the mark by Delroy Facey.
49 mins: Knight was offside just 10 yards inside their Cambridge half - the home side were playing a very high line.
46 mins: Perez collected Kenny Irons' shot.
A dull and shapeless first half saw Cambridge fight hard and close the Terriers down at every opportunity to prevent them from playing their usual game.
Chances were few and far between with Schofield and Thorrington peripheral figures as the Terriers struggled to overcome their energetic hosts who never looked like threatening Martyn Margetson's goal despite troubling Clarke and Gray from time to time.
44 mins: Knight was fit to play on and trotted back onto the pitch.
42 mins: Knight was winded after he was felled by a rough challenge. Alex Moreno wanted Knight to be stretchered off during a long stoppage.
40 mins: Cambridge broke free after Jackman made an interception. Irons and Kenkins argued as to who was responsible afterwards.
38 mins: Town won a corner after Irons cut inside and hit a shot which was deflected away.
37 mins: Facey was onside and going for goal before the ball was put out for a throw-in.
35 mins: Town won a free kick after Knight was bundled off the ball.
33 mins: Clarke had to be quick to sweep in the threat after Wanless found space behind Gray.
32 mins: Town were penalised after Gray was wrongly adjudged to have fouled a Cambridge player.
32 mins: Tudor won the corner and Jackman delivered a left footed outswinger but Facey headed clear.
31 mins: Irons was goalside but was pulled down in the 'D' as the offside trap was beaten. The referee didn't give a foul!
30 mins: Cambridge were closed down by Holland who broke up the Abbey Men's attack.
28 mins: Facey was flagged offside after a superb ball from Kenny Irons fell to the big Town striker but a late offside flag foiled Facey as he went one on one with Perez.
26 mins: Wanless' scissors kick flew just wide after Town allowed Cambridge onto them. Margetson was livid after Town's defence switched off.
25 mins: Facey tried to get behind Goodhind with a header but the game was poor as Cambridge stopped most of Town's midfield traffic with a hard-working performance.
23 mins: Town were defending deep again.
20 mins: Thorrington's twisting run and chancy shot was charged down with Knight waiting vainly in the area for a cross. Schofield latched onto the rebound but his chance was saved.
19 mins: Gray cleared with a very poor and wayward ball as Irons looked on despairingly from just yards away, waiting for a pass.
17 mins: Cambridge won another dengerous free kick with their attacking football after Holland went in with a tough challenge.
15 mins: Tom Youngs was defied by Chris Holland's boot as he hit a goalbound header only to see it cleared.
14 mins: Cambridge were working hard to close down the space in the centre of the park. Town were coping well but things were getting competitive on the pitch...
10 mins: Tudor was fouled by Schofield for a dangerous looking free kick near the area. Margetson bowled the ball out to Facey but the Town striker over-ran it was wasted the attack. Town had to be alert to repel the counter-attack.
9 mins: The ball smacked straight into Clarke's face.
8 mins: Gray was penalised for a foul on Wanless.
7 mins: Clarke's goalbound header was grasped by Perez. The young defender was unmarked and had time to place his header - the Terriers were working hard and closing the home side down effectively.
6 mins: Goodhind interecpted a cross meant for Knight and conceded the corner.
5 mins: Thorrington's persistence won a throw-in as Town started a flowing move but the Abbeymen eventually intercepted the ball.
4 mins: Town were sitting deep as they soaked up the early Cambridge pressure.
3 mins: Thorrington hit a pass for Knight but it was shepherded out of play.
1 min: Cambridge came out with attacking edge, Gray cleared from a throw-in.