A last-minute stand-in at Wimbledon qualifying, Australian Alex Bolt has stormed to the men's main draw, sealed by an "unreal" comeback triumph from match point down in his final round.

The green-and-gold challenge was further boosted on Thursday as Olivia Gadecki also made it into the big show at SW19 next week by winning her third-round women's singles at the cut-throat Roehampton qualifying event to ensure there'll be 13 Aussies at the grass-court grand slam.

Bolt, the 31-year-old South Australian from Murray Bridge, produced one of the "top two" performances of his tennis life to rally from two sets down, surviving a match point, to beat rising Swiss Leandro Riedi 6-7 (7/9), 2-6, 7-6 (9/7), 7-5, 6-4 and book his place among the SW19 elite next week.

"You couldn't write a better script for the journey I've had this week," beamed the Davis Cup veteran.

For it was the culmination of a wholly improbable tale, with Bolt, on the alternates list, having resigned himself to missing the qualifiers on Monday, only to be called at 10.50am to replace a late withdrawal, Monaco's Valentin Vacherot, for an 11am start.

He went on to beat Argentina's Nicolas Kicker 6-1, 6-4 and then, on Wednesday, defeated German Rudolf Molleker by the same scoreline.

Yet the great adventure looked doomed as Riedi, two sets up, held a match point at 6-5 in the third-set breaker on Thursday.

Instead, Bolt produced a "clutch" serve, the launchpad for a tremendous comeback in his first five-set match in more than four years as he prevailed after a draining three-hour 41-minute duel.

"Just super proud of my efforts just to hang around in the match," he said.

"I let opportunities in the first set slip and I kind of let that take control of my mind for the next hour and a bit, and then he got the second set as well playing really good tennis. I kept hanging around, managed to turn the tides … yeah, unreal."