Chinnor suffered a cruel 27-24 defeat at Clifton in a second round game they looked to have had in the bag.
Six minutes into injury time, they were in control of both the match and the ball.
Four points to the good, Chinnor had intelligently driven into the Clifton 22.
The ball reached Rewi Tolich, who was hauled down just a metre short.
It looked game, set and match to Chinnor and justifiably so as they had played much the better rugby in the second half.
But an unkind ricochet bounced into the hands of Clifton full back Kent, who won a kick and chase covering the entire field.
With Barnes converting from the touchline Clifton had snatched victory from the jaws of defeat.
The referee later indicated that had Chinnor kicked the ball dead in their final phase, he would have blown up, making the result an even bigger pill to swallow.
With Matt Buckley and Raaki Maxwell injured, and Mike Cook unavailable, James Hewitt played full back, Philip Seymour made his starting debut, and versatile club captain Jon Brooks joined the back-row.
Clifton led through Barnes's first minute penalty and he converted Levis's try six minutes later.
Eric Brown then forced his way over for Chinnor and Richard Williams converted.
Some sloppy defending allowed Sills go over with Barnes again adding the extra points.
A flowing move up the touchline saw Rewi Tolich score and Williams converted Brown's second to see Chinnor leading 19-17 at the break.
Clifton hit back through another Barnes penalty, before Brown completed his hat-trick with a powerful run down the wing on 60 minutes.
Williams missed a penalty, but the game looked safe at 24-20 until the dramatic injury-time twist.
Paul Hennessy's leadership was again first-rate, ably supported by Joe Winpenny who put in another sound performance.
Seymour, Ben Hackshaw and Ed Devine, who all played for Chinnor's Colts last year, also impressed.
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