Supposedly marked with the initials "WL" carved into its bark in May 1813, the often controversial tourist tree came crashing down on Saturday afternoon, February 20, with little public fanfare.

The eucalypt was at first a landmark tree, then a stump, above the Great Western Highway about five kilometres west of Katoomba for 208 years.

Fearing a landslip that might block the highway corridor and push cars into a ravine, transport engineers closed the road and urgently removed the ageing monument before forecast rain.

If the historic stump had collapsed it would have taken its heavy stone platform with it. The amputated tree's top half was missing anyway, and it was held together with steel straps.

Many years ago, concrete was poured inside most of the stump in an effort to protect it.

But were all the earlier efforts worth it? Well, yes.

To many mountain residents, especially from 1876 onwards, the stump was a "living" memento of the first attempt of inland colonisation. By late 1903, the relic was considered unique (even if unsafe) and, of course, a travel destination to boost early local tourism.

However, an interpretive display was built near the tree's site at Pulpit Hill two years ago reminding viewers of the impact of colonialism on the Dharug and Gundungurra peoples.

Maybe the once significant tree had had its day by 2021? Everyone suspected it was surviving only on good luck amid changing times.

European explorers Blaxland, Lawson and Wentworth paved the way for future Sydney settlers when they discovered a way over the top of the previously impassable western mountain barrier in 1813.

But by the 1880s "their" marked tree looked dead. A wall and fence was erected in 1884 to preserve the tree, a tangible relic of the pioneering days. But, in recent decades, it has been vandalised, survived an arson attack (in 2005) and bushfire, and a vehicle severely damaged the monument in 2012.

Blue Mountains Council is now trying to relocate the tree remnants.

But while there have always been doubts about the historic tree's authenticity, it had remained, until now, a potent symbol of a past era.

Oddly enough, there's a surprising Novocastrian link to the Explorers Tree, if the once sketched, now long-gone, initials carved into it were actually "WL", as claimed.

William Lawson was one of the three hardy explorers finally able to cross the Blue Mountains in 1813. Lawson was also once a commandant of the Coal River (Newcastle) penal settlement for about a year, circa 1809.

However, his time here is mostly remembered these days for one epic struggle: conducting a battle of wills with a "depraved" and troublesome Irish playboy convict.

Better known perhaps is that the successful 1813 expedition by the intrepid trio lent heavily on six earlier failed expeditions, including one by exiled French surveyor Ensign Francis Barrallier, who had originally mapped the Lower Hunter in 1801.

Blaxland, Lawson and Wentworth followed the mountain ridges, while earlier explorers, including Barrallier, set out from Sydney following the valleys. This always ended with the expeditions being thwarted as they ended up facing sheer sandstone cliffs.

While on the subject of historic marked trees, let's return to explorer Barrallier.

How about there's not one, but two lost trees of explorers in the Hunter Valley? Barrallier was on the survey mission that penetrated the Lower Hunter's interior by boat almost as far as Greta in 1801.

In 2009, a party of explorers from the University of Newcastle climbed Mount Elizabeth, off Maitland Vale Road, to make the unexpected, accidental discovery high up of an old, dead, ringbarked tree with a long vertical scar on its trunk.

While there's no proof it was one of the two lost explorers trees from 1801, the blazed tree met all the tests, including its position in line with the river. And, because it was so far up, it seemed unlikely that it was an Aboriginal canoe tree or even a boundary marker.

But, without any positive scientific proof of the tree's age, it's all speculation. That situation remains unchanged to this day. (The second tree was never found.)

Meanwhile, there's another tree monument much closer to home. It's the "Fishing Tree" (pictured), featured prominently in the foyer of the Newcastle Museum in Honeysuckle.

The large tree is estimated to have lived for up to 400 years, until 2001 when it was burnt by vandals. It once stretched over the water at Bagnall's Beach, Nelson Bay. It was used by generations of Worimi people to find schools of passing fish. Footholds can still be seen along the trunk. A finder would climb the tree, look into the water and direct people in ingenious and sturdy bark canoes.

They fished with lines made from waterproofed bark, or with spears made from Gymea lily stems and four prongs of ironbark.

But now, let's end with another puzzle, this time west of Sydney, on the edge of the giant Blue Mountains sandstone ramparts.

It again involves the energetic early Hunter explorer, Ensign Barrallier.

In late 1802, Barrallier was instructed by colonial governor King to find a way across the Blue Mountains to allow for expansion of early Sydney Town.

It failed, but not for want of trying.

With others, the explorer travelled about 100 miles (161 kilometres) by foot in seven weeks before being stopped by foreboding cliffs and a waterfall, now known as Barrallier's Falls.

Barrallier also marked a tree with an X along the route set out in his journals. Does it still exist after 219 years? After all, much of the bush is still untouched, being part of the enclosed Warragamba Dam catchment.

Lake Macquarie bushwalker and author Greg Powell tried to solve the matter by retracing the steps of Barrallier's expedition over six days in the early 1970s.

"It's wild country, very isolated and hard to get in. It's total wilderness. We never expected to find anything by the time we reached the waterfall," Powell said.

"We had a cursory look around there before hacking our way out. By then, we couldn't waste time, couldn't dilly-dally.

"The falls are in Christy's Creek which flows into the Kowmung River, which then flows into the Cox's River. The area's below Kananga Walls. But no one else has found Barrallier's tree either as far as I am aware.

"In his journal, all written in French, the explorer says the going was so tough that their boots were torn and their clothes shredded, and it was with great reluctance they turned back. It was very disheartening, but he was within a day of success if he persisted and he'd got on top of Kanangra Walls," Powell said.