The tree now. "In December 2016, our soon-to-be new neighbours advised us in person that they thought our eucalypt was 'unsafe' and suggested it should be removed," Mr Robertson said. The couple sought the advice of an arborist the next day and two days later, the arborist inspected the tree. The arborist discovered that three of the tree's key structural roots, each up to 16 centimetres in diameter, had been severed, 1.1 metres from the tree base and on the neighbouring property. He said the cuts were clean and had been done with a chainsaw or similar implement.

One of the severed roots. The arborist advised the tree had been healthy and sound and of low risk, but the severing of the roots so close to the stem had rendered it unsafe. Worse, had he been consulted prior, he said, he would have been able to recommend a likely safe distance at which the roots could have been cut. The tree originally. The tree was now unstable and, given its enormity, represented an immediate danger to life and property.

The next day, the couple took urgent action on the recommendation to cut the tree down. It was difficult to get contractors to do this, given it was so close to Christmas, and the couple eventually ended up spending the holiday period watching a team of men spend four to five hours to reduce their tree to a five-metre stump. The arborist explained the stump would not be able to support any new growth. WAtoday has viewed the arborists' invoices totalling $850 and the bill of almost $5000 to cut the tree down. The couple said that after the discovery of the cut roots, they ran into their soon-to-be neighbours on the block next door. They alleged their neighbours displayed some local council information on their mobile phones, which said they were within their rights to sever any roots encroaching on their property.

They then contacted the building manager, who confirmed the building plans did not warrant root removal and that the action had not been undertaken by him or his subcontractors. The couple twice wrote to their neighbours to ask whether they had cut, or paid someone to cut, the tree roots and if so, on what evidence of danger or nuisance. In the second letter, they asked for financial compensation. The arborist had used the Australian Thyer Tree Valuation Method and the tree's original dimensions to estimate a dollar value of more than $26,000. The couple had sought quotations for the purchase, transport and planting of a mature replacement tree of that species. The largest available, a 10-metre specimen, could cost up to $30,000.

In their letter, the couple asked if the matter could be finalised informally, or if not, through mediation. They mentioned that they hoped to put this behind them and resume normal neighbourly relations. In February, they finally received a letter from the neighbours' lawyer that denied any cutting of tree roots, but nevertheless emphasised they were lawfully entitled to cut encroaching tree roots if they chose. The identity of the person who cut the roots remains unknown. The couple has now resorted to engaging a lawyer who drafted a letter to the neighbours on Tuesday claiming damage and financial losses.

Legal Aid WA's website says anyone cutting a neighbour's tree root on their side of the property should "take care not to cause unnecessary damage". New South Wales and South Australia have tree or tree-owner protection law but WA does not – instead, the responsibility is delegated to local councils. The City of South Perth has a Significant Tree Register featuring similar lemon-scented gums. "Our tree's ratings on height, girth, and canopy as well as its ratings on other National Trust attributes such as age, landscape value, community opinion, scarcity, potential threat, and wildlife habitat, mean it would very likely have qualified as a Category One Significant Tree. Significant Trees in the COSP are given Tree Protection Orders requiring COSP approval before they are pruned or their roots impacted in any way," Ms Gillieatt said. The couple will need to remove the stump at some point, work that has been quoted at $1600.

Loading For the moment, they see the stump's presence as a monument to the damage done. The couple has joined the South Perth Urban Tree Network, recently formed in line with similar community groups in Victoria Park and Stirling. Follow WAtoday on Twitter