Oliver Tarvet set up a second-round Wimbledon showdown with Carlos Alcaraz after a sensational win over Leandro Riedi.
The world No733, from St Albans, came through three rounds of qualifying to book his place in the main draw, in what is his first appearance at a tour-level event.
Tarvet did not face a single break point on Court 4 and showed no signs of nerves as he secured a 6-4 6-4 6-4 over his Swiss opponent, who had also come through qualifying.
He will now face Alcaraz on Wednesday, after the defending champion survived an almighty scare to beat Fabio Fognini in five sets.
Arthur Fery will join his fellow Briton in the second round, after the welcome produce a stunning upset to see off 20th seed Alexei Popyrin in a 6-4 6-1 4-6 6-3 victory. Italian Luciano Darderi is next up for Fery.
Cameron Norrie and Billy Harris also progressed on a strong day for the home favourites, but there were defeats for Jacob Fearnley, Oliver Crawford and Henry Searle.
There was no mistaking the joy Tarvet felt following his win, the 21-year-old punching the air with a wide smile plastered on his face after serving out the victory.
"There's a lot of emotions, just really overjoyed. All the hard work I put in the last few years has clearly paid off,” Tarvet said.
"It's my first tour-level event, to come out here, come through qualifying, win a first-round match, have a chance to play maybe Carlos on Wednesday, it's just a dream come true."
Tarvet is guaranteed at least £99,000 after reaching the second round, though he will be unable to claim most of that due to college rules in the United States.
Players are allowed £7,290 in profit every year from professional tournaments, limiting Tarvet as he competes under the National Collegiate Athletic Association (NCAA) system at the University of San Diego.
On the prize money issue, he said: "I've got to find more and more on expenses by the day. We'll see. I'm not here for the money, I'm here for the crowd and the experience and just to stamp my mark. I think I've done a pretty good job so far."
Speaking last week, Tarvet said: "I know there have been complaints about it but I don't want to speak too much about it and overstep the mark.
"But in my opinion, I've worked hard to get this money. I don't feel like it's undeserved the money that I've got.
"I think it would be good to see a change in the rules of the NCAA, but at the same time, I don't want to get involved. It's not really my place.
"But I've done well this week. I think I deserve this money."
There was more success later on Monday for the home favourites, as Norrie came through a tricky first-round match against Roberto Bautista-Agut.
Norrie, now the British number three behind Jack Draper and Fearnley, beat the Spaniard 6-3 3-6 6-4 7-6 in just over three hours.
Bautista-Agut served for the fourth set at 5-4, but Norrie broke back and forced a tie-break, which he won 7-3. He will next face 12th seed Frances Tiafoe.
Barely a minute later, Fery joined him in the second round.
The 22-year-old lost in the first round when given a Wimbledon wildcard for the last two years but made it third time lucky here, as he earned his first main-draw win at a Grand Slam.
It was an impressive one, too, with Fery getting the better of Popyrin, sinking to his knees and punching the air as the Australian sent a forehand long.
Billy Harris then took the tally of British men through to the second round to four with a straight-sets win over Dusan Lajovic.
This was the 30-year-old’s first-ever victory at Wimbledon and earns him a second-round match against Nuno Borges.
Fearnley endured a more frustrating afternoon as he was beaten in straight sets by Joao Fonseca on Court One.
After being comfortably second-best in the first two sets, Fearnley took the third to a tie-break and held a 5-2 lead, but lost five points in a row to fall to a disappointing first-round exit against the Brazilian teenager.
Wildcard Crawford was also knocked out despite a strong start.
The 26-year-old took the opening set against Mattia Bellucci in a tie-break but could not do more than that, as the Italian recovered to win 6-7 6-3 6-4 6-4 and he will now play Queen’s finalist Jiri Lehecka.
Like Crawford, Searle won the first set against American Ethan Quinn before losing the second, and the match then turned on a tie-break.
There were three set points in it for 19-year-old Searle but he could not take any, as Quinn won the tie-break 13-11 and went on to secure a 4-6 6-2 7-6 6-3 victory.
