The Bexhill-based player won the final five frames to turn a 5-1 deficit into a 6-5 first round victory against world number three Ding Junhui.
Fernandez, ranked 130, said: “It’s an amazing feeling to beat a player as good as Ding. When I was 5-1 down I was thinking about having to get the train home, but I hadn’t played badly.”
Two-time UK champion Ding rattled off six breaks of more than 50 to win five of the first six frames, but Fernandez took it to a decider with a break of 80 and then sealed victory with a brilliant final pink.
The Ireland-born player has been struggling with a slipped disc in his back and said he was in a fair amount of pain at the York Barbican. He will face Thai potter Noppon Saengkham in round two.
Fernandez returned to the tour in August having served a 15-month ban after admitting corruption charges and had not won a match this season.
The 41-year-old achieved a highest world ranking of 67 and the best result of his career was his run to the last 16 of the 2003 Welsh Open. He won the English Amateur Championship in 2011, a year after moving to Bexhill from London.
The area’s two highest ranked players will be in UK Championship first round action later today.
Jimmy Robertson, the world number 37 from Bexhill, will face Maltese cueman Alex Borg this afternoon after St Leonards-based Mark Davis, ranked 40, plays Chinese potter Xu Si this morning.