Leamington made life hard for themselves before progressing to the last eight of the cup at the expense of their near-neighbours, writes Paul Okey.
Substitute Josh March proved the match-winner, firing home from close range in the last minute of normal time on a night when four of the five goals stemmed from corners.
It was a cruel end for Banbury but they could count themselves fortunate to still be in the tie after a one-sided opening 40 minutes in which the gulf between the Conference North and Southern League was painfully apparent.
With Callum Maycock pulling the strings in midfield and Dexter Walters seeing plenty of the ball, Brakes penned the Puritans back in their own half for large spells as Mike Ford’s side repeatedly coughed up possession.
The first decent chance for Brakes came in the tenth minute when Walters’ cross to the far post picked out Jordan Murphy who volleyed into the ground and away from goal.
Kieran Dunbar put a measured shot straight at visiting keeper Jack Harding, while Walters saw an effort deflected for a corner as Brakes stepped up the pace. George Carline should have done better after being released by Murphy on the right but after cutting into the box, his tame shot slid past the far post, gaining a slight deflection from a defender in the process.
From the resultant corner, Connor Taylor then saw his stooping back header drift agonisingly past the far post.
With 24 minutes gone, Brakes finally got their reward. Maycock cleverly spread the ball wide to Walters who cut inside, beating two defenders before seeing his shot deflected on to the bar by a despairing defender. Murphy then had the simplest of tasks to head into an empty net from six yards.
Stephan Morley put a free-kick into the wall and Murphy slid a shot across goal as Leamington pressed for a second before Banbury produced their first effort on goal, Jaanai Gordon failing to guide his shot on target from the angle of the box.
A spell of Banbury possession in the 37th minute ended with another cheap giveaway but Walters was unable to produce a finish to match his piercing run.
The home side could count themselves unlucky to only be a goal to the good as half-time approached such was their dominance. However, rather than taking a slender lead into the interval they found themselves trailing.
The equaliser had a touch of fortune about it with Haysham’s corner ricocheting in off the head of James Mace at the near post under pressure from Jack Westbrook.
Lifted by the goal, Banbury were back on the front foot from the restart and a neat turn and shot from Haysham was gathered at the second attempt by Jake Weaver.
A Westbrook shot from distance was then diverted wide by Lane for a corner which Brakes again failed to deal with.
Weaver made a complete hash of the delivery and Gordon was quickly on to it, getting in a shot that was deflected into the path of Connor Roberts who made no mistake from close range.
Leamington were sent out early for the second period but did not have it all their own way in the opening skirmishes.
Harding was out bravely at the feet of Connor Taylor after a Walters cutback and play quickly switched to the other end where Weaver was swiftly off his line to smother an effort from John Mills.
Gordon was off target with a shot, while Mace was close to a second own goal after his rushed clearance from a Gordon cutback landed on the roof of the net.
Weaver was again flapping under the resultant corner but there was no one to take advantage for the visitors.
A corner was again the source as Brakes got back on terms just past the hour-mark, Lane’s header back steered home by Mace from a central position six yards out.
Banbury substitute Mo Ahmed struggled to get into the game after his introduction but his first meaningful contribution should have led to a third for the visitors. However, Mills could only clear the Harbury Lane End stand from the winger’s astute cutback.
The winner again came from a corner, this time needlessly conceded by Banbury with a miscued clearance from Harding compounded by Eddie Odhiambo’s wild header back over the dead-ball line.
Dunbar’s initial cross was returned to him and his second delivery pinballed around the box before March drilled it home from the penalty spot to keep alive hopes of a third Birmingham Senior Cup trophy in four years.
Brakes: Jake Weaver, George Carline, Stephan Morley, Callum Maycock, James Mace, Jack Lane, Jordan Murphy, Callum Gittings, Conmor Taylor (Josh March, 73), Kieran Dunbar, Dexter Walters (Jack Edwards 78). Subs not used: Kaiman Anderson, Joe Clarke, Ben Newey.
Banbury: Jack Harding, Connor Roberts, Kynan Isaac, Jack Westbrook, Charlie Hawtin, Pablo Haysham (Eddie Odhiambo, 83) Claudio Dias, Lee Henderson, John Mills, Morgan Roberts (Mo Ahmed, 68), Jaanai Gordon. Subs not used: Gedeon Okito, Craig Fasanmade, Charlie Barnett.