Revitalised Cheltenham Town arguably produced their best performance of the season to notch their first win in ten outings and move off the bottom the table.
This was certainly their brightest night since the reverse trip to the U’s Abbey Stadium back in October, and it got off to a flier when Shaun Harrad scored after only two minutes.
They had hit the bar, had one disallowed and saw a good shout for a penalty waved away before they were undone by the type of error that has undermined their season, this time by Trevor Carson 12 minutes before the interval.
But on this occasion they didn’t allow it to deter them, quite the opposite in fact.
They came back out for the second half in determined mood and found two more through Danny Haynes, the night's star performer, and Matt Sparrow, both claiming their first goals for the club.
This fantastic result will fill the players, management and supporters with renewed belief ahead of Saturday’s trip to Johnson's former club Northampton Town that they can bridge the one-point gap to safety with just three games to play.
There were four changes and a switch in formation for the visit of Richard Money’s side following the 2-1 defeat at Wycombe Wanderers.
Bristol City loanees Wes Burns and Jordan Wynter limped out of the match at Adams Park and missed out here, meaning Haynes and Harrad were recalled into the starting XI.
They were joined by Matt Taylor, in for Jack Deaman and Zack Kotwica who took the place of Shaquille McDonald. Both took their places on the bench which featured just six players because of injuries throughout the squad.
Johnson matched Cambridge man for man, deploying a 4-4-2 formation and his side made the perfect start, scoring in only the second minute to get Whaddon Road rocking.
It was vital that Cheltenham started well, and the goal came about when Harrad had raced onto a measured ball by Haynes and fired home into the bottom right-hand corner from 16 yards to put his side on the path to victory.
It was a swaggering start, and they forced Cambridge into all the defending in the opening exchanges.
It could have been two five minutes later, but Danny Haynes lifted his effort over from a tight angle down the right.
Cambridge responded, but Harrison Dunk was wayward with three efforts and Ryan Donaldson shot wildly over from a 25-yard free-kick.
The Robins were in the ascendancy and played with real confidence, and were unrecognisable from the side that had performed so meekly in recent outings.
There was a moment of magic from Kotwica approaching the half-hour mark, cutting in from the left and unleashing a fine right footer but unfortunately for young winger, it came back off the right post.
It fell nicely for Mathieu Manset who bundled home, but the big man had strayed into an offside position and the goal was chalked off.
The Frenchman shot on the turn a moment later, but it travelled a foot wide of the left upright.
At this point Cambridge had barely carried a threat but they made the home side pay for not converting their dominance into a second goal by grabbing a 33rd minute equaliser.
Ryan Bird scored it, meeting Dominic’s Ball’s delivery from the right with a flick. Carson allowed it to squirm through his grasp, and failed to reach it at the second attempt and the mistake dented his side’s bright opening to the match.
At the other end Harrad was in determined mood, and acrobatically volleyed a foot over two minutes before the break, when Lee Vaughan was replaced by Durrell Berry after the right back had collected a muscle injury during the first 45 minutes.
Cheltenham made an equally purposeful start to the second half and there were early openings for Matt Richards, Haynes and Harrad before Haynes stretched the Robins’ lead 12 minutes after the restart.
Craig Braham-Barrett forced a corner down the left, swung to the back post by Sparrow. Taylor met it with a towering downward header and the former Ipswich Town, Charlton Athletic and Bristol City man slammed home from close range.
He was causing the Cambridge defence all sorts of problems and went on to send in a series of wicked crosses that with any touch would have resulted in a third goal. Manet went closest, but couldn’t guide his effort on target 20 minutes from time.
Cambridge made a couple of changes to try and disrupt the momentum built by the Robins, but they couldn’t contain Gary Johnson’s side and with 15 minutes to play they extended their lead through Sparrow.
Braham-Barrett sent in a throw from the left, not the chest of Harrad who with his back to goal attempted to juggle the ball into a shooting position. It ran loose, but Sparrow smashed one from the edge of the box and beat Chris Dunn, the Cambridge number one, with a heavily deflected half-volley to give his side some breathing space.
There was a scare when substitute Sullay Kaikai took advantage of Troy Brown’s slip, but Carson atoned for his earlier mistake to push the effort wide.
Sparrow then saw a late chance fizz past the right post on the stroke of time.
CHELTENHAM TOWN (4-4-2): Carson; Vaughan (Berry 46), Taylor (c), Brown, Braham-Barrett; Haynes, Sparrow, Richards, Kotwica; Subs not used: Mills, Gould (Gk), Deaman, Sterling-James, McDonald.
CAMBRIDGE UNITED (4-4-2): Dunn; Ball, Coulson, Nelson, Taylor; Mendez-Laing (Morrissey 78), Champion (c), Donaldson, Dunk (Kaikai 65); Elliott (Slew 65), Bird. Subs not used: Tait, Norris (Gk), Hunt, Simpson.
REFEREE: G Sutton
ATTENDANCE: 2,415 (212 from Cambridge)