Martello Launches Official CON29M Report – Why It Matters More Than Ever

With collapsing driveways, cracking foundations and unexpected sinkholes, mining legacy risks are re-emerging across the UK – not only in the coalfields, but in growing towns and cities too. For conveyancers, these events are a stark reminder that mining risk is no longer a “historic” concern – it's a live one. Martello’s newly launched official CON29M report is designed to meet this moment. It’s the clearest, smartest mining risk report available to the UK property market – and it’s launching just as mining risk is becoming impossible to ignore.

Martello is now an official Law Society–licensed provider of the CON29M – the mandatory coal mining search for property transactions in affected areas. But our version isn’t just a compliance checkbox. It’s built to solve long-standing frustrations shared by conveyancers, estate agents, lenders and buyers alike.

We launched this product because too many conveyancers were telling us the same thing: the CON29M was often unclear, incomplete or too binary. It either returned a vague warning, or it passed without context – leaving lawyers and their clients in the dark. So, we set out to build something better:

• More checks, fewer failed reports
  Martello runs additional analyses upfront to minimise ambiguous results. More checks means more certainty – reducing the number of transactions delayed by “refer for further investigation” responses.

• Expert interpretation on every high-risk case
  If a risk is flagged, it doesn’t get auto-reported – it gets assessed by a real human expert. This extra layer means we reduce unnecessary worry and provide practical next steps.

• Built by leading geo-risk specialists
  Our report was co-developed by Tom Backhouse, founder of Terrafirma and one of the UK’s leading authorities on ground risk. The goal: deliver the CON29M that conveyancers have always needed but never had.

• Better visuals and better communication
  Our reports are clear, visual and written in plain English. No more legalese or unexplained “risks.” You’ll see the mine entries, understand the potential impact, and know exactly what to tell your client.

• Same price, wider coverage
  The price stays the same whether your site is 1 or 30 hectares. And it comes with £1m Loss of Value insurance included.

In short: we released this report to raise the standard. Because risk is rising – and the current status quo isn’t good enough.

Mining risk isn’t just a curiosity from Britain’s industrial past. It’s right under our feet. Over 11% of UK properties are in coalfield areas, with millions built near mine shafts.

What’s more, these aren’t remote hillsides or brownfield fringes. Today’s cities – Birmingham, Leeds, Newcastle, Manchester, Cardiff, Glasgow – all grew around coal. As they densify, so too do the risks. More basements, deeper foundations, heavier loads. All on top of ground that may once have been hollow.

We tend to think of mining risk as something that affects old houses. But some of the UK’s most alarming subsidence cases have involved brand new homes – often built without adequate investigation of the ground beneath.

Case 1: Bayfield Estate, Newcastle (2016–17)
A brand new housing development built over shallow, unrecorded coal workings began to crack and fail. Within months, five homes were demolished, with ten more condemned. Families were evacuated. The Coal Authority paid out over £3 million – its largest ever compensation case.

Case 2: Merthyr Tydfil, South Wales (2018)
A sinkhole opened on a brand new estate road, cutting off access. It exposed gas and water infrastructure, and left residents stranded. The site had a long mining history, but the development was marketed as safe. Mining searches weren’t mandatory.

Case 3: Flintshire and Wrexham (2022–23)
An FOI request by the BBC revealed 14 subsidence incidents in 18 months across just two counties – including active collapses, remediation works and insurance claims.

Each case illustrates a simple truth: if you don’t check, you won’t know – and that can cost thousands.

Even where a property has stood for decades without issue, today’s climate extremes are introducing new pressures.

• Wetter winters are saturating soils and triggering collapses in old mine voids.

• Hotter summers are drying shrink–swell clays, increasing the rate of subsidence.

• Flash floods are washing out old shaft caps, culverts and drainage systems that weren’t designed for modern conditions.

Insurers saw a major spike in subsidence claims after the 2022 heatwave – the hottest UK summer on record. But that’s just the beginning. The British Geological Survey has warned that extreme weather will drive a sharp rise in ground movement in years to come – including mine-related collapses in previously unaffected areas.

You’re not a mining engineer. But your client expects you to spot the red flags. And with lenders increasingly aware of subsidence risks, skipping the right checks isn’t just risky – it could be negligent.

A proper CON29M should give you more than compliance. It should give you:

• Clear, plain-English risk summaries

• Maps that show exactly what’s nearby

• Expert context that saves you hours

• Fewer failed reports

• Happier clients and faster transactions

Martello’s report does all of that – without the delays and ambiguities you’re used to.

Mining risk is on the rise. But with the right tools, it doesn’t need to derail your deal.

Get in touch with us directly at hello@martello.app.