It was April of that year when his son, Michael, burst into the house to tell him about a brick that had been found in the vicinity of the old rail tunnel off Vera Street.

"He said, 'I think it's the platform'," recalls Mr House, the head of Helensburgh Landcare Group.

"And I went down and said, 'it's definitely the platform'."

Metropolitan Colliery had been clearing out some 80 years' worth of mud, silt and rubbish that had buried the train platform two metres below the surface.

Excited about the historical significance of the find, Mr House supervised the excavation of 40 truckloads of soil waste and replaced the train tracks that had been removed when the line closed.

For about a decade, locals and a handful of in-the-know photographers had the place all to themselves.

That lasted until 2010, when Mr House said a resident made a video about the spectacular glowworm population residing within the tunnel next to the platform and posted it to YouTube.

With the build-up of silt at the entrance to the tunnel reaching about halfway up the portal, the rare species - found only in Australia and New Zealand - had been accumulating over decades.

Helensburgh had always known about the glow-in-the-dark walls, with local kids climbing across all the debris to gain entry.

But now the whole world knew about them.

"People come from everywhere, they come from overseas, they come from interstate and it's been a disaster for the locals," said Mr House, 77.

If he could have a do-over, he would play no part in restoring the rail line.

"I wish we had just left the tunnel as it was, but I was doing it as a historical focus rather than the glowworms at that stage," he said.

"The history of the line was fundamental to the decisions that I made: the platform was the only platform sandwiched between two tunnels in Australia," he said.

"But it hasn't been a happy story."

Over the past few weeks, members of the Helensburgh Glow Worm Tunnel Facebook group have posted pictures that show torches being directed at the bioluminescent creatures.

An exasperated Jo Smith, chair of the local glowworm tunnel committee, once again reminded the group about the rules in place to protect the sensitive colony, one of the biggest in the southern hemisphere.

"We just ask you to respect the land and ecosystem around the tunnels," Ms Smith wrote.

"ALL torches or lighting is to be shone upon the ground ONLY!

"Shining bright lights into the tunnel will detrimentally affect the glowworms. They are extremely sensitive and the light will affect them."

For Ms Smith, who grew up in that part of Helensburgh, the ongoing degradation of the site is personal.

"As kids we used to go through the bush and it was just this pristine, beautiful place that no one but pretty much the local kids knew of - and maybe their parents," she said.

"So it was sort of like a place lost in time.

"It's about the history of my town, and it's about the uniqueness of the glowworms.

"It makes me angry because I've told people on this site many, many times these same messages and people don't read them and they just go in there and have no respect.

"They just ignore the rules or they're ignorant of the rules."

Death of the glowworms?

The carelessly aimed torches - which result in an inferior viewing experience because darkness is needed to see the glowworms properly - are just the tip of the iceberg when it comes to issues facing the site.

There's the environmental toll from the busloads of tourists, many of whom arrive wearing inappropriate footwear for the slippery, muddy terrain and end up wrapping plastic bags around their shoes.

Hundreds of these shopping bags are then dumped on the ground on the way out, despite the council bin near the parking area.

Then there's the anti-social element, which has proved an endless nightmare for neighbours.

"They started doing graffiti, they damaged the railway sign, they started doing fireworks inside the tunnel and recently we heard that a couple of louts went into the tunnel on motorbikes," Mr House said, pointing out the tracks in the mud.

"I know that people have been doing fancy fireworks in there for photography purposes, like lighting up a steel wall and spinning it around, and setting fireworks off because of the huge echo."

By 2018, the din coming from the tunnel at night (not to mention the rubbish left around or put in neighbours' green bins) had become so intolerable for residents that Crown Lands erected a fence in a bid to appease them.

Landcare, who manages the site, left the gate open during the day and closed at night, until COVID hit and it was permanently locked.

"And it was not very well liked by people, who cut the bolts with angle grinders," Mr House said.

"They climbed over the fence, which was very dangerous. They were not very nice."

Worried about visitors injuring themselves on the pointy metal tops, Landcare asked for the fence to be removed in 2022, which has left the group with few options for protecting the unique natural wonder.

The group is looking into security cameras, while new signs outlining the do's and don'ts of visiting the sensitive area are due to be erected at the tunnel in the next week or so.

Mr House said there were also plans to put up a fence partway down the 500m-plus tunnel in order to stop people from going to the "dangerous" end.

To be able to see the glowworms during the day, people must walk about 30 metres past the end of the rail tracks, where it becomes just mud and eventually water, like a lake.

"I've actually walked to the far end of the tunnel, which is a big concrete plug, and the mud gets to the point where you put your foot down and you can't pull your foot out without leaving your gum boots behind," Mr House said.

"And then you've got to try and retrieve your gumboot out of the mud ."

There's no need to go that deep at night as the glowworms come out along the top of the tunnel all the way to the entrance and even appear in the vegetation outside.

"We keep telling people you're wasting your time going during the day, come at night and you'll see them and more safely," Mr House said.

"But the downside of that is, of course, if visitors come at night, they start disturbing the neighbours because they're not exactly quiet."

Mr House strongly urged the public to change its ways so the extraordinary light spectacle was still around for future generations.

"All of these activities are basically going to lead to a diminution of the glowworm population," he said.

"And if it continues at the levels that it's going at the moment, because it's a very highly visited area, we may even see the local extinction of the species in this tunnel."