Gwennan Harries harbours mixed emotions. Almost simultaneously she feels a little bit nervous, extremely excited, cautiously optimistic and, most definitely, envious. “It’s the biggest game in our history,” says the former leading Wales striker as she prepares for BBC punditry duties at Rodney Parade where, on Friday, Jayne Ludlow’s side face Phil Neville’s England. “I would have loved to have played in a match of this magnitude.”

Harries is not guilty of hyperbole. After all, Ludlow’s predominantly semi-professional Wales are a point ahead of the vaunted, fully professional Lionesses at the top of the pair’s World Cup qualifying group. Only one side are guaranteed automatic qualification.

Should Wales triumph, they will qualify for next year’s finals in France, leaving Neville’s squad hoping to enter the play-offs as one of the best four runners-up across seven groups.

“It’s a once-in-a-lifetime opportunity,” says Harries, who won 56 caps before a knee injury prefaced retirement three years ago. “And the pressure’s all on England. I’m a bit nervous but I can’t wait.”

Although Neville’s players have a potentially decisive game in hand – their final group fixture is in Kazakhstan on Tuesday week – Wales have still to concede a goal in qualifying. When they drew 0-0 with England at Southampton in April, Neville, taking charge of his first World Cup qualifier, conceded it “felt like a defeat”.

The Welsh FA’s decision to stage the return at the 7,850-capacity home of League Two Newport County has attracted English criticism for a perceived lack of ambition but Ludlow believes an atmospheric ground familiar with FA Cup upsets maximises her side’s chances of progression to a first World Cup finals.

“A lot of fuss has been made about Rodney Parade but winning this game could be life changing for the Wales players, so it would have been a bit silly to play somewhere bigger which would have made it easier for England,” says Harries.

“It’s about something much more important than playing in front of maybe 30,000 at Cardiff. Around 75% of Jayne’s squad are still semi‑pro, many doing full-time day jobs, but now they have the chance to be the first Welsh football team to reach a World Cup finals since the men in 1958. Rodney Parade was sold out within 24 hours, which is huge. We’ve never had interest like this before; our previous record crowd was around 4,000.

“I don’t think Jayne looked at playing the game at a bigger venue, and rightly so. Ninety-nine per cent of coaches would do the same and choose a ground offering them maximum advantage. England reached the semi-finals of the last World Cup and the last European Championship; they’re ranked fourth in the world. You’ve got to make it as hard as possible for them.”

Harries hopes her country can capitalise on England’s potential teething troubles with their new tactical blueprint under Neville. “I was a little bit surprised at Southampton,” she says. “Wales were never carved open. I thought England’s manager would switch tactics in the second half but Phil Neville didn’t change anything.”

Former Wales striker Gwennan Harries says the match against England is a “once in a lifetime opportunity”. Photograph: BBC

When the Lionesses did apply concerted pressure, Cardiff’s Laura O’Sullivan, then of Cyncoed Ladies, repelled everything thrown at her and much now may hinge on Ludlow’s goalkeeper-cum-full‑time office administrator reprising such heroics.

“Jayne’s squad are mainly office workers and students but a few, like the Watford striker Helen Ward, combine football with motherhood,” says Harries, who has helped make the BBC documentary Women in Red about the Wales players’ off-field lives. High-profile professionals such as Natasha Harding of Reading and Jess Fishlock – a midfield teammate of England’s star striker, Jodie Taylor, at Seattle Reign – are notable exceptions.

Rachel Rowe, until she recently turned professional with Reading, served as a full-time prison officer, making the 300-mile round trip between her Swansea home and the team’s Berkshire training ground three times a week. Her fellow forward Kayleigh Green, newly professional at Brighton, spent last season training as a plumber. Olivia Clark, O’Sullivan’s student understudy, represents Lincolnshire’s Nettleham Ladies.

“Going so long without conceding a goal is testament to the manager’s tactics and the players’ discipline, dedication and hard work,” says Harries, whose fluency in her native tongue enables her to teach PE at a Cardiff school proud that Welsh remains its first language. “Wales are incredibly well organised, they defend from the front and their teamwork is fantastic. Wearing that red shirt is so special to everyone.”

When Ludlow played in Arsenal’s midfield – with a Roy Keane-esque intensity – she enhanced her fitness by spending time off running up the forbidding Rhigos mountain in the Rhondda Valley. Now that “no brick walls” philosophy has spilled over into management. “Playing in the same team as Jayne, I was sometimes quite fearful,” says Harries, only half joking. “But her passion creates a fantastic team spirit.”

Not to mention sparking a revolution in the country. “When I started playing at school I was the only girl and joined a boys’ team,” says the 30-year-old. “Now there are lots of girls’ teams. The uplift in interest in the last three years has been phenomenal but the big thing is that Jayne’s players are inspiring girls to believe they can succeed in sport – and life.”

Wales also aim to reacquaint Neville’s side with failure. “England are under a new kind of pressure these days,” says Harries. “They’re expected to do well and that’s not always easy to cope with. I’m quietly confident. I think we’ll win.”