New South Wales Metro captain Oliver Davies has become the first batsman in 17 seasons to score a double-century at the Under 19 Male National Championships in Adelaide.

Davies, 18, scored an incredible 207 from just 115 balls in a mammoth total of 4/406 for NSW Metro during a 168-run win over Northern Territory on Monday. He cleared the boundary a tournament-record 17 times including six sixes in one over.

The NSW Metro skipper also reached the boundary 14 times. Davies became the first batsman to make a double-century in a one-day match in the history of the Under 19 National Championships.

Former Australian Test spinner and NSW Blues player Jason Krejza was the last batsman to reach the magnificent milestone at the Under 19 national titles in a two-day game during 2001/02.

The right-hander said he had never hit six sixes in one over.

“After the first two sixes, I sort of had in the back of my head that I wanted to try and give it a crack,” Davies said.

“It paid off in the end.

“(My aim during the over was) to target forward square to cow corner.

“Just getting down on the back leg before it was even bowled, just trying to slog sweep them over mid-wicket.”

Davies said it was an amazing feeling to hit the ball so cleanly in the first match of the tournament for NSW Metro.

“Going out to bat today, (reaching 200) wasn’t at the forefront of my mind, obviously I was hoping to put up a big score … for the team.

“After setting an early base for myself, I just took it from there and hit them pretty well.”

The Manly-Warringah batsman in McDonald’s NSW Premier Cricket said his only other double century came in junior cricket at Under 13 level.

WATCH: Ollie Davies on U19 Championships double ton.

Last season, Davies became the second player born in the 21st century to score a hundred in NSW Premier Cricket, when he made 119 for Manly-Warringah at 17.

His NSW Metro Under 19 team mate, Mosman batsman Lachlan Hearne, beat him to the post by one week. He became the first millennial to score a First Grade century against Campbelltown-Camden.

Davies said the best thing about his double century on Monday was that it contributed to such a big total for the team.

“To first of all lose the toss and get sent into bat, on what seemed to be a little tricky to start on, the ball sort of came on nicely and to put on 406 is a great effort,” he said.