“It’s massive, that was the nice blend of all the team – myself, coach Yu Hiu-tung and Karan – we’ve all played at this level and it all helps when you’re there with a young team,” said Walker, who played for HK in the late eighties and nineties when they competed in Group I, the furthest they’ve gone.

“Hong Kong are showing a lot more depth, we’ve got other young players who weren’t at this tie and it’s nice to see young players coming through – it is important to have experience around them too and Karan, myself and Tung have been there and done it.

“And for an 18-year-old in Jack to go out and play his first ever five-set Davis Cup match away from home and win just shows how much he has matured and is starting to have some real belief – that’s the biggest thing in the transition from junior to senior level, understanding the physical demands but also to be professional disciplined and prepare well.

“There’s a real promising future for some of these players and it’s not by accident, the Tennis Association has invested in a lot of things to make this happen.”

Hong Kong went to Thailand for a training camp ahead of the tie and Walker hailed the team’s physical strength and mental resilience as they battled to victory in 30-plus-degree heat and stifling humidity. He pointed out that in all three rubbers they won, they had to fight back from losing the opening set on tiebreak.

“It was a long trip but a good one,” said Walker, who came back to Hong Kong as director of player development in 2016 after more than 20 years away.

“We had all four players participate and with the format of the Davis Cup at this stage being best of five sets, it’s a very different ball game to what everybody’s used to in division three with three-set games – physically and mentally it’s much, much tougher.

“We had an established doubles pair in Karan and Kevin who reached the final of two Futures tournaments in December, that allowed Jack and Andrew to go out and give everything they had on day one.

“We went to Thailand for five days’ training before and that really helped, we were very clear on our strategy, knew what we were doing before we arrived, and physically and mentally were very well prepared.

“It’s a good lesson for the youngsters that you put in the work and you get the rewards.”

Jack Wong got Hong Kong off to a perfect start when he battled past Thien Nguyen Hoang in five sets over nearly three and a half hours, 6-7 (4/7), 7-5, 6-3, 3-6, 6-0.

Former Wimbledon Boys Doubles champion Nam Hoang Ly beat Li in straight sets (6-1, 6-2, 6-4) before Rastogi and Kevin Wong put HK ahead again in the doubles, 6-7 (7/9), 6-4, 7-6 (7/4), 6-1. Ly levelled the tie against Jack Wong (6-3, 7-6 (10-8), 6-4) setting up the decider for Rastogi and Nguyen Hoang.

Former ATP Tour player Rastogi, now a coach with the HKTA, represented India for several years in the Davis Cup and his experience – and freshness, with Vietnam using only their top two players – told as he won 6-7 (7/4), 6-1, 6-2, 6-1.

Hong Kong now travel to Pakistan to face the top seeds in April for a place in the final. Thailand and the Philippines are in the other semi. Pakistan were relegated in a play-off from Group I last year and have massive experience, with their top two players having played 86 ties between them.

“It’s obviously going to be a tough match in Pakistan, we’ll see who’s available from our players in American universities,” added Walker.

“Kevin and Andrew both made themselves available for this one which is great but it can be tough to get the time off.”