Elite Human Judgement,
Rebuilt as Software.
An early warning system for property investors.
It catches the deal you are about to lose, the value you are about to miss, and the refurb you are about to stall, before it costs you.
Pre-Seed SEIS Round · Advance Assurance Pending · Sentinel is a trading name of Sentinel OS Ltd.
The easy version of this business is over.
Cheap Debt Is Dead
Higher rates, Section 24 and rising stamp duty broke the maths of passive buy-to-let.
The Old Playbook Is Breaking
93,000 landlords exited in 2025. Passive buy-to-let no longer works. The edge moved to repositioning and value-add.
Complexity Has Increased
Planning angles. Lease structures. Operational overlays. Property became a judgement game.
In a harder market, execution becomes the edge.
Investors don't fail for lack of knowledge.
They fail on execution.
There has never been more property education. Yet committed investors who understand the fundamentals keep making the same expensive mistakes. The gap isn't what they know. It's what they do under pressure, against the clock, with real money on the line.
Delayed Deals
A good deal sits while they hesitate. Someone else buys it.
Flawed Appraisals
Optimism creeps into the numbers. A "great deal" loses money.
Missed Value
The lease angle, the layout, the planning play. Walked straight past.
Execution Drift
A live deal goes quiet the way dead deals go quiet. Lost before anyone notices.
The real problem isn't the bad decision.
It's that the same three failures keep repeating.
Opportunity Cost
Found the deal. Lost the deal.
Quiet for two weeks. Then exchanged, to someone else.
Actual Cost
Bought an asset. Got a liability.
Bleeding cash, no exit, no buyer at the right price.
Missed Value
£100k+, walked straight past.
Lease re-gear. Planning reclassification. Layout split. Operational overlay.
Sentinel sits over the investor as they work a deal.
Learns You
Capital, timeline, risk appetite, strategy. The starting picture.
Reads The Deal
Comparables, lease terms, vendor signals. Sentinel builds the full picture in minutes.
Finds The Value
The lease angle, the layout, the planning play. The unlock most investors walk past.
Catches The Drift
A live deal goes quiet. Sentinel interrupts, unprompted, with the move to make today.
That interruption is the whole product.
A real-time execution loop,
built by a fighter pilot.
In the cockpit, the pilot with the fastest, most accurate decision loop wins. It is called the OODA loop. Sentinel runs that loop continuously, for property investors.
Observe
Capture what the investor actually does, not what they say they will do.
Orient
Read behaviour against known failure patterns. Spot the signature of a deal going wrong before the investor does.
Decide
Surface the highest-risk moments first. A ranked warning, not a to-do list.
Act
The right intervention, at the right moment, before the window closes.
Most tools track activity. Sentinel maintains execution.
The moat compounds with every deal.
Pattern Library And The Founder Behind It
Defensible now. A decade of knowing how investors fail. A competitor cannot download it or prompt it into an LLM.
Instrumentation
What this round builds. Turning observation into software that logs and measures every action.
What Compounds: Behavioural Intelligence
Every user makes the system better at catching the next user's mistake. Earned through use, not claimed on day one.
The Endgame: Prediction
Recognising the signature of failure before the investor sees it. The warning arrives before the mistake.
The model is the commodity. The judgement and behavioural data on top are the proprietary assets. AI getting better helps us.
Built on a proven business and operational prototype
Coaching Revenue
2025. A profitable business proving real demand in the exact market.
Paying Members
A warm audience that already trusts the founder with their money.
Weekly Active Users
On Unicorn OS, the no-code first version of Sentinel. Real engagement.
Deals Tracked
Inside the first version. The behavioural data the engine learns from.
"I'm blown away by the EOS you're building. I believe I can get at least one more deal at a better price by using Sentinel."
Peter Bright, Property Entrepreneur
"It's like you were talking directly to me about procrastination, overwhelm and lack of momentum. This will help a lot of us."
Stuart Cleevely, Property Investor
Founder-market fit, the rarest ingredient.
Rob Stewart — Founder & CEO
RAF Fast-Jet Pilot
Tactics instructor. High-stakes execution under pressure.
Ascent Flight Training
Lockheed Martin / UK Gov. Scaled training systems nationally.
20 Years in Property
Investing and operating across the full UK market cycle.
Decade of Coaching
Hundreds of investor journeys. The pattern library, built deal by deal.
The RAF taught the discipline. Property produced the patterns. Sentinel turns both into software.
Twenty years of judgement. The engineering to build it.
Sadan Masroor — Founding Engineer
Booking.com
Senior Software Engineer, Backend Chapter Lead. Built and scaled backend systems at one of the world's largest tech platforms.
Mastercard Foundation
Lead Architect for five years. Designed the microservices architecture behind global fintech infrastructure.
14+ Years in Production
Python, Elixir, Kubernetes. From prototype to systems running at scale, end to end.
Selected Among the Best
One of three developers chosen from oDesk's premium service providers to work directly with Silicon Valley startups.
Rob built the pattern library. Sadan builds the engine it runs on.
Large, fragmented, and professionalising fast.
2.84M+ UK Landlords
The Total Market
In the UK's £1.5 trillion private rented sector. (HMRC, Savills)
443,272 Professionalising Investors
Sentinel’s initial beachhead
Scaling investors operating through Ltd Co structures
Up 66,587 in 2025 alone. (Hamptons, Companies House)
~1,000 Active Users
This round’s milestone target
At ~£97/month, that's £1.1M+ ARR
1,000 users is the proof point, not the ceiling. The market is 443,272 professionalising investors and growing.
£250,000 to prove the engine.
Terms
Use of Funds
Beyond Property: The Execution Gap is Everywhere.
High stakes, high pressure, complex decisions where hesitation costs real money. This isn't unique to property investing; it's the same pattern in every domain where judgement under pressure decides the outcome.
Financial Decisions
M&A, underwriting, capital allocation.
High-stakes decisions where judgement quality determines outcomes.
Pipeline & Performance
Sales, recruitment, sourcing.
Success depends less on opportunity flow, and more on consistent execution.
Operational Execution
Complex projects, delivery, transformation.
Where momentum stalls, priorities drift, and costly mistakes compound.
Same engine. Same pattern library. New domains. Property proves it first.
Sentinel.
Elite Human Judgement, Rebuilt as Software.
Twenty years of pattern recognition. Built into software that watches every deal, and interrupts before it's lost.
The pattern library exists. The pilot cohort is ready. £250,000 builds the engine.
Sentinel