The Northern Irishman teed off in the final group in Hertfordshire and delivered a course record 63 to sit at eight under par, nudging ahead of six players locked at seven under.
David Howell rolled back the years and looked to have earned his first 18 hole lead at a European Tour event in 636 appearances as he joined Australian duo Jason Scrivener and Min Woo Lee, Zimbabwe's Scott Vincent, Hero Open runner up Thomas Detry and Laurie Canter as co-leader.
But the 27-year-old Sharvin, who graduated to the European Tour after finishing the 2019 Challenge Tour season in 11th position on the Road to Mallorca Rankings, carded ten birdies and two dropped shots to take the outright lead.
"It was a nice round, played really well, didn't do too much wrong," Sharvin said.
"Put it on the fairway, hit a lot of good shots and holed a few putts as well and it all added up to 63. Pretty happy to start well.
"A long way to go but it's always nice to shoot a good score on the first day and not put yourself out of it."
Hanbury Manor Marriott Hotel & Country Club returned to host a European Tour event for the first time in 21 years and it did not disappoint as 92 players broke par.
Howell was amongst the late starters in Hertfordshire but turned in 31 thanks to birdies at the first, third, fourth, seventh and eighth to move into contention.
Another gain at the tenth saw the five time European Tour event winner join a swell of players at six under, one shot behind the leaders which grew to a group as big as seven during his back nine.
Canter, playing three groups ahead of Howell, jumped ahead to nine under thanks to back to back birdies from the 15th, only to card a double bogey at the tricky 17th.
As Canter dropped back into the fold at seven under, Howell nudged himself into the sole lead courtesy of a hole out at the par four 15th for an eagle two.
However, he bogeyed the penultimate hole - the only blot on his card - to drop back to seven under.
"It's been a long time since I've put a good first round on the board to be honest," Howell said.
"It's what I've been crying out for. I've played some reasonable golf in spurts since we've come back but haven't got off to a great start.
"Today it happened so it was lovely. Nice to see my name somewhere near the top of the leaderboard, if not the top."
Scrivener was the first player in the clubhouse to card 64 as he opened up with a birdie at the second but had to wait until the seventh to pick up his second shot, which sparked a hat-trick of gains to reach the turn at four under.
Further gains at 12th and 14th moved him to six under before a 20 foot birdie putt at the next moved him alongside leader Adrian Otaegui, who then left the Australian on his own at the top when he bogeyed the 17th hole.
Scrivener was desperately unlucky not to extend his lead after brushing the edge of the cup with birdie attempts at the last two holes, but he was joined at the summit by compatriot Lee.
Lee, who missed the cut at the first two legs of the six week UK Swing, made a superb run of birdies around the turn to move into contention.
The 22-year-old picked up two shots and carded a bogey in his first four holes before his birdie trail began at the eighth and finished at the 12th to surge up to six under.
He parred his way to the 18th before rolling in his eighth birdie of the day to reach seven under.
Vincent went quietly about his business after a disappointing opening bogey and replied by picking up shots at the third and fourth.
An eagle at the ninth saw him turn in three under but he was flawless on the back nine, gaining strokes at the 11th and 14th before a birdie-birdie finish saw him increase the group at the top to three.
Detry, runner-up at the Hero Open last week, banished those memories with a confident performance which started with birdies at the second and third before four in a row from the sixth.
The Belgian, who has yet to win on the European Tour, dropped a shot at the 11th only to regain it at the next.
And when Detry sent his approach at the 15th to within five feet and rolled another birdie putt, he was tied for the lead.
Fellow Belgian Nicolas Colsaerts broke out of the pack to move to eight under after a nice approach at 15th but was joined by Canter after he eagled the 12th.
Colsaerts and Canter bogeyed their respective next holes before the former hit a double bogey to drop further back, while the Englishman moved back ahead.
Detry slipped to six under with a dropped shot at the 17th but picked it back up at the last.
But the low scoring did not stop there as Sharvin picked up momentum after a birdie-birdie-birdie start.
A bogey at the fifth set him back but he replied with gains at the seventh and ninth to get to four under.
Back to back birdies from the 11th propelled Sharvin to one off the lead, only to drop a shot at the 13th.
Consecutive birdies at the 14th and 15th increased the leading group to seven before he rolled in a third gain in a row to take the lead on his own.
Jack Senior, who teed off in the opening group and turned in 29, was one 12 players to be two shots of the lead, which included Danish rising star Rasmus Højgaard, South African Brandon Stone and Colsaerts.