Goals from Kieran Agard and Aden Flint – each their 12th of the season – made it 15 games unbeaten for the Championship-bound Robins, who can now look forward to receiving their trophy next Sunday against Walsall at a sold out Ashton Gate.There was also joy for the beaten hosts though, as results elsewhere meant Chesterfield’s place in the Sky Bet League One play-offs was confirmed with a game to spare.Steve Cotterill made one enforced change to the team that clinched the title last week, as Jay Emmanuel-Thomas replaced the injured Aaron Wilbraham for his first start in just over a month. With George Saville returning to Wolves following the expiry of his loan spell, only five players were available on the bench for City’s first-ever visit to the Proact Stadium. Whilst City’s fate was sealed at Bradford 11 days ago, Chesterfield still needed points to cement their play-off place. The reverse fixture showcased attacking football of a high intensity, but the opening exchanges of this one proved unpredictably low-key. It took 18 minutes for the first chance of the match to arrive as both sides looked like cancelling each other out. Joe Bryan found space 25 yards out, took a touch out of his feet but fired his effort into the home fans behind the goal.When Marlon Pack’s loose pass allowed Jay O’Shea to feed the ball into Jimmy Ryan’s path inside the box, it looked likely Chesterfield would grab the opener but Frank Fielding responded with a fine save, utilising his legs to force the ball to safety.Bryan warmed the gloves of home keeper Tommy Lee with a stinging shot at his near post.But when Chesterfield were caught out over-playing just outside their own box on 31 minutes there was nothing Lee could do to prevent Agard from breaking the deadlock. The former Rotherham United forward danced his way past Sam Hird and slid the ball under the keeper’s onrushing body as calm as could be.Almost immediately O’Shea headed an effort towards Fielding’s near post from 12 yard out and again the City number one had to be at his best to keep it out.Before the interval Agard had another chance, from a similar position to his opener. This time Emmanuel-Thomas threaded the pass into the box but Agard’s first-time attempt dragged along the ground and Lee saved well.After the break City continued in the ascendancy as Emmanuel-Thomas again was the provider, this time playing in Luke Freeman only for the League One Player of the Season contender to slip at the vital moment.The result looked to be all but confirmed when Flint grabbed the second on the hour. Rising high above even the keeper’s full stretch, the lanky forward sent Pack’s floating corner into the net with a bullet-like finish.Chesterfield fell flat from that moment on, as City passed the ball around to cheers of “ole” from the1,600-strong travelling fans – who even started their own conga .There was a brief scare at the death when O’Shea rolled a free kick into Roberts’ path and his arrow-like drive crashed against the crossbar with Fielding beaten all ends up.