City ran out 3-0 winners in a hectic M4 derby to take a significant step towards promotion at the expense of their local rivals.
Kieran Agard, Joe Bryan and Aaron Wilbraham did the damage with three expertly taken goals in a fine team performance in which City also defended manfully for long periods.
Steve Cotterill revealed Mark Little would miss the rest of the season after announcing James Tavernier as his starting right wing-back an hour before kick-off.
The manager had remained coy on the injury sustained by the defender in the Good Friday draw at Oldham Athletic in the build up to the game.
It was a frenetic start to a match with no shortage of tension between two sides who had not parted ways on the best of terms at the County Ground five months ago.
Two teams usually so assured in keeping possession were trading attacks quickly.
Luke Freeman tried his luck inside the opening 30 seconds with a rising drive that comfortably cleared Wes Foderingham’s crossbar.
City’s intentions were clear from the start and Freeman combined with Bryan to force a corner at the end of a rapid counter-attack soon after.
But Swindon proved themselves just as adept on the break when they found themselves four against three, only for Nathan Byrne to take the wrong option in shooting against the advancing Korey Smith with options to his left.
The visitors were creeping more and more into the contest and must have been wondering how they had not taken the lead with a flurry of chances around the 20-minute mark.
First Aden Flint was guilty of a rare mistake against his former club to allow Andy Williams to steal in, but Swindon’s top scorer was denied by a stooping Frank Fielding save with Michael Smith better placed in support.
Fielding would endure a busy spell in the City goal, saving from Ben Gladwin’s 20-yard shot before Massimon Luongo’s attempted volley was headed over his own bar by Marlon Pack.
Then Fielding had to make the best save of the lot when Smith flicked a right-wing corner goalwards and wheeled away only to be stopped in his tracks by a brilliant one-handed stop high to the keeper’s right.
Even after City had survived the temporary onslaught, Yaser Kasim had Ashton Gate hearts in mouths when his ambitious 40-yard free kick just dipped a split-second too late.
Cotterill’s men did well to hang in there at that point and would reap the rewards for their resilience later in the half.
Swindon survived loud penalty appeals on the half-hour when Flint was clearly held back in heading a Smith cross off target from six yards.
Then a Freeman delivery was headed out only as far as Smith, whose goalbound volley struck a defender with Foderingham rooted to the spot.
But the breakthrough would arrive nine minutes before the interval as Agard helped himself to his tenth league goal of the season and surely the most important so far.
City’s high pressing game caught the visitors off guard, winning the ball deep inside the Town half near the left touchline before Freeman supplied Agard, who lifted the ball brilliantly over Foderingham and into the roof of the net as the keeper rushed out.
Swindon would have felt hard done by to be behind at that point and came within a whisker of levelling things up just before the break.
Gladwin, who was proving a real nuisance, cut in off the left flank and drove a shot towards the far corner cleverly flicked on by the stooping Williams and against the underside of the crossbar with Fielding for once well beaten.
Swindon’s pressure continued into the second half. Kasim was presented with another free kick opportunity, this time only half as far from goal, but sent his shot into the wall.
Luongo fired over when left unopposed on the edge of the box and Williams sent an even better chance over as City dropped further back towards their own goal.
The Swindon front two almost combined to goalscoring effect as Smith headed wide from a Williams cross, before City began to pose questions of their own at the other end.
Bryan sent a brilliant low cross fizzing across the six-yard box that required emergency action from Jack Stephens facing his own goal, slicing the ball into the air before it dropped on to the top of the crossbar and behind for a corner.
Then Flint charged in at the back post to meet Pack’s corner from the left but again looked to be impeded by Rossi Branco as the chance came and went.
But City would not be denied, as Bryan curled in a superb second goal ten minutes from time before Wilbraham added gloss to the scoreline from yet another Freeman assist.