Sydney’s inner-west is familiar with neighborhood disagreements, but a prolonged feud in Balmain over fixing a brick boundary wall might be among the priciest so far.

Professor Catherine McMahon, an academic at Macquarie University, along with her spouse Neil Bryant, has issued a $60,000 bill to their neighbor for repairs done on a shared wall in 2022.

The letter, drafted by attorneys representing McMahon and Bryant, included a clause imposing a 29 percent monthly interest on any unpaid amount—potentially escalating the debt into the millions if applied.

After just one year, the total would climb past $1million.

The letter also warned that if builders were denied or delayed access to carry out the work, the neighbour would be charged $250 an hour plus GST.

The dispute reportedly started when McMahon and Bryant accused the neighbor and their workers of using sledgehammers to tear down a section of the shared brick wall, against an engineer’s advice to use a diamond-blade saw to gently separate the connected walls.

McMahon and Bryant the rough demolition damaged their side of the structure, which also served as a retaining wall between the properties. 

They allege  the neighbour then failed to stabilise or repair the wall, causing further deterioration and inflating the eventual repair bill.

After the alleged damage, the couple issued a formal ‘Notice to Carry Out Fencing Work’ under Section 11(1) of the Dividing Fences Act 1991 (NSW), demanding that their neighbour contribute to the cost of rebuilding.

The demand, sent through law firm Lion Legal, included the builder’s quote for the work and the steep penalty clauses covering interest and access delays.

Lion Legal solicitor Nasir Hanafi, acting on behalf of Professor McMahon, declined to comment due to ongoing proceedings.

The matter is expected to be heard in court next month.

The case has reignited debate over the financial and emotional toll of neighbourhood conflicts, particularly in tightly packed suburbs like Balmain. 

Lawyer Andrew Carpenter said the case serves as a cautionary tale for homeowners that even seemingly minor property issues can escalate into complex and costly legal battles.

Mr Carpenter said he had witnessed people lose their homes over a neighbourhood dispute. 

‘I did one recently where there was a $13,000 fence, and both parties spent in excess of $200,000 on legal fees over this,’ he said.

‘Fencing disputes can be a lot like family law, where it’s based on emotions rather than economic sense. 

‘These people are going to be spending more on legal fees than what the fence is worth.’ 

In this latest case involving the sky-high interest rate, he said that while parties are free to set their own rates in private contracts, courts can step in if the rate is deemed excessive. 

Mr Carpenter said generally the interest that can be claimed before a court judgement is made, is the RBA cash rate plus 4 per cent. 

‘The only time that you can attempt to claim a high interest rate would be if the parties have signed a contract before agreeing to a specific interest rate,’ he said.

‘But even if that’s the case, courts can then set them aside if they seem to be manifestly excessive. 

‘What we’ve seen in recent times is people believe that they know the law, and they issue letters claiming absurd costs or interest rates which simply are not enforceable in court.’

Mr Carpenter said lawyers were bound to act on their clients instructions so if the client demanded a 29 per cent interest rate then the lawyer was bound to act.

‘If you’re doing something like this to your neighbour, it’s going to firstly, sour the relationship, but secondly, it’s going to make you look silly, because there’s no way in hell a court will ever enforce interest rate like that,’ he said.

‘It’s just a scare tactic, but it’s also unenforceable, because I don’t see anyone that can justify 29 per cent per month at interest rate for for a fence repair.’

It isn’t the first time the prestigious Balmain postcode has made headlines for high-stakes neighbourly feuds. 

In 2019, a long-running dispute between residents escalated into defamation claims, AVOs, and even a segment on A Current Affair. 

Lawyer Vanessa Hutley was ordered to pay her tradesman neighbour $300,000 after a bitter row over a fence ended in a rant on national TV.

Ms Hutley accused builder Anthony Cosco of bullying her and her family and making their lives ‘hell’ during an A Current Affair segment in June 2016.

Mr Cosco launched defamation proceedings against Ms Hutley following the segment. 

Justice Stephen Rothman ruled Ms Hutley had bullied and defamed Mr Cosco and had ‘displayed an abysmal arrogance and sense of privilege’.

The dispute began when Mr Cosco moved into his $1.75million home in 2013 and began erecting a tall fence between the properties.

In the years to follow, their dispute escalated to the point that both parties took out AVOs against each other.

Mr Cosco had pleaded guilty to malicious damage after he sprayed expanding foam into a vent which led to Ms Hutley’s property after she refused to move it.