The 19-year-old from County Meath showed a cool head and confident style as he took the Burton & Smith Amateur Derby on 9-2 favourite Tender Falcon.
The race, run each year over the same course and distance of the world's most famous race, can be a test of the skills of the less-experienced jockeys who take part.
But among the riders in its hall of fame are such names as present-day trainers Philip Mitchell, Andrew Balding and Luca Cumani along with many others who have gone on to make their name in the sport.
Always in touch, Tender Falcon took control of the race over two furlongs out when striding into a clear advantage.
Flying Spirit and Simon Walker tried to rally inside the closing stages but their efforts still left them a length and a quarter adrift of the winner at the line.
Desert Island Disc plugged on to take third under Scott Dobson.
Winning trainer Ron Hodges admitted that the booking of Lynch for his mount had not exactly been the result of a well-hatched plan.
"I didn't realise that we had to choose a rider I thought it was done by ballot so they sent me a list of the ones I could choose from and there were only five left out of the 12," said Hodges.
"It just so happened that Liam Cashman's daughter rang me about something else and when I asked about him, she said that he was quite good.
"I did a bit of research into him and he sounded all right so we gave it a go and he did as he was told. Well, almost.
"That's the thing with these amateurs, they take responsibility and they don't come back full of excuses when they get beat!"
Lynch was bringing his career tally of successes to 10, several of which have come in point-to-points.
He aims to turn professional next year after completing his studies.
Frankie Dettori enjoyed a topsy-turvy afternoon as he rode a double for Godolphin before crying off his final three mounts through illness.
Dettori struck first when Atlantic Story took the opening EBF Roger White Maiden Stakes.
The 8-1 chance was quickly away under the Italian and held on well in the closing stages of the seven-furlong contest to beat Rumbalara by half a length.
Dettori loves nothing more than entertaining a Bank Holiday crowd with a winner or two and he completed a quickfire double wrapped up with a standing dismount when Sights on Gold took the JRA Golden Jubilee Conditions Stakes.
The well-backed even-money favourite was keen in the early stages but eventually settled nicely on the heels of leaders Island Sound and Crystal Curling.
Martin Dwyer kicked on aboard Crystal Curling on the home turn, but Dettori always had the move covered on the winner and steadily came to make his challenge at the furlong-pole before drawing clear. Battle Chant, struggling early on stayed on best to grab the runner-up spot.