Oxfordshire amateur Craig Hinton suffered a nightmare as he ran up a 12-over-par 82 on his Open Championship debut at Royal St George's.
The 22-year-old from Thame dropped eight shots going to the turn in 42, including a quadruple bogey eight at the 495-yard fourth.
He then suffered four more bogeys on the inward nine to come home in 39.
But fellow Oxfordshire golfers Adam Wootton and tour pro Gary Boyd both fared better, each carding one over.
"I was very pleased with a 71," Wootton told BBC Sport. "I was a little bit nervous on the first tee, but as soon as I'd made a couple of putts and got a birdie at three, I settled down."
Wootton, 23, from the Oxford Golf Centre, made three more birdies in the easier afternoon conditions, at 6, 10 and 14.
But he also dropped shots at the fourth, 11th and 15th, as well as running up a double bogey at the 13th.
Hinton, who plays at The Oxfordshire, did well to qualify, having overcome major health problems this year.
He spent a week in intensive care earlier this year with myopericarditis, an inflammation of the heart.
And, in 2009, he endured temporary blindness in Jerez while travelling in Spain with the England amateur team.
Hinton, who goes out for Friday's second round at 1505 BST, was one of three Oxfordshire golfers in the field at Sandwich.
Tour pro Boyd, from Banbury, started well with a first-hole birdie, then, after dropping successive shots at 4 and 5, picked up another birdie at the seventh to reach the turn in level par.
He was then back to one under at the 14th before dropping two more shots at 15 and 18.
Boyd returns for his second round on Friday at 1048 BST, while Wootton goes out in the game before at 1037 BST.