Classic car security: why older cars are easy to steal and what actually stops it

Here is an uncomfortable fact about a car built before the late 1990s: it can be stolen by someone with a screwdriver, a length of wire and three minutes, and nothing on the car will object.

That is not a design flaw. The cars were built for a world where theft meant joyriders, where a door lock was a deterrent and an ignition switch was a switch. The world changed around them. Organised theft for export and for parts now targets precisely the cars that have the least protection and the highest value per kilogram, and a good classic is both.

The good news is that the same simplicity that makes a classic easy to take makes it straightforward to protect, provided you understand what the various devices actually do rather than what the marketing implies.

Why there is nothing there to defeat

From the mid-1990s a European directive required every new passenger car to be fitted with an immobiliser, defined as a device intended to prevent the vehicle being driven away under its own engine. Member states could refuse to register non-compliant new cars from the late 1990s onward, which is why the immobiliser became universal at around that point.

Everything before that date is a different world. A typical British classic has a mechanical door lock, a steering lock on later cars, and an ignition switch wired in a way any workshop manual describes. There is no electronic handshake between key and car, nothing to clone, nothing to relay. Thieves of modern cars need laptops; thieves of classics need patience and a quiet street.

So the question is not how to fix the electronics. It is how to add layers to a car that has none.

What the Thatcham categories actually mean

Thatcham Research tests and certifies vehicle security products to defined criteria, and its categories are the vocabulary insurers use. They are widely misquoted, so here they are as Thatcham defines them.

Category 1 is an electronic alarm and immobiliser together. Category 2 is an electronic immobiliser on its own. Category 2-1 is an alarm added to an existing Category 2 immobiliser to reach Category 1 status. The immobiliser specification is the same across these: it sets itself passively, isolates at least two operating circuits or one relevant control unit, and resists attack for a minimum of five minutes.

Category S5 is a vehicle tracking system. Its stated purpose is to detect unauthorised use of the vehicle and to increase the chance of recovery. It is monitored around the clock and includes a driver identification device and motion detection, so the monitoring centre can raise an alert if the car moves without the owner’s tag present.

Category S7 is an asset location system. Its purpose is narrower: to increase the probability of recovering a stolen vehicle. It is also monitored around the clock and must be able to locate the vehicle within a mile in general terrain and pinpoint it within fifteen minutes of a signal being received. It does not require a driver tag or motion detection, so it cannot itself flag that the car is moving without you.

The S categories replaced the older Category 5, 6 and 7 from 1 January 2019, so any guide still quoting “Cat 5” is describing the previous scheme.

Two corrections to claims you will read elsewhere. There is no Thatcham category called “S5 Plus”; that is vendor language. And remote immobilisation, the ability to stop the car from a control centre, is not part of the S5 specification. Where it is offered it is an add-on, and worth asking about separately.

The tracker is not the defence

A tracker does nothing to prevent theft. It is a recovery tool, and a good one, but by the time it is doing its job your car is in the back of a van. Its value depends on the monitoring centre’s response, the police’s capacity to act on a location, and whether the thieves have already found and removed it.

For a classic that argues for a tracker as the last layer rather than the first. The layers that stop the theft happening are cheaper and less glamorous.

Mechanical immobilisers. The Association of British Insurers recommends them because they do two things no electronic device does: they are visible from the pavement, which makes the thief pick a different car, and they physically prevent driving even if the ignition is defeated. A steering wheel lock, a pedal lock or a gear lever lock, used every time, is the single most cost-effective thing a classic owner can do.

A hidden battery isolator or fuel cut-off. Cheap, invisible, and baffling to a thief who has just hot-wired the ignition and cannot understand why nothing happens. On a car with a simple loom these are a home-mechanic job.

An electronic immobiliser. A modern Thatcham-rated immobiliser can be fitted to most classics by a specialist. It gives the car the protection it never had from the factory, and it is the device insurers most commonly ask about.

An alarm. The ABI’s guidance is that alarms act as a strong deterrent to opportunists and that owners of older vehicles should consider fitting one. On a classic, the subtler value is waking you up.

Where it sleeps. Most classic thefts are from driveways and streets. A locked garage, a locked gate, a post, a second vehicle parked across it, and security lighting all change the calculation for someone who needs a quiet few minutes. Storage is security, which is one reason the two questions come up together so often.

What the insurer is actually looking for

Classic insurance is written on the assumption that the car is garaged, driven modestly and looked after, and the security questions follow from that. Insurers typically want to know where the car is kept overnight and whether it has an immobiliser or tracker, and on higher-value cars may require an approved device as a condition of cover.

The point worth taking from Thatcham’s own wording is that certification does not guarantee insurer recognition; that is negotiated device by device. So ask the insurer which specific products it recognises before spending money, and get any security condition on the policy in writing, because a condition you have not met is a claim you will not get paid.

The numbers, honestly

Police recorded 312,250 vehicle offences in England and Wales in the year to March 2026, down eleven per cent on the year before, according to the Office for National Statistics. That figure bundles theft of vehicles, theft from them and interference, across every car on the road.

What does not exist is an official figure for how many stolen classics come back. The absence is worth noticing: it means nobody can honestly promise you a recovery rate, which is another argument for spending on prevention first and recovery second.

A sensible layered setup

For an ordinary classic of ordinary value, the combination that addresses most of the realistic risk is a good mechanical lock used religiously, a hidden isolator, and a garage. For a valuable car, add a rated immobiliser, and if the value justifies monitoring costs, an S5 tracker with a driver tag. Ask the insurer which devices it recognises first, fit what it recognises, and keep the paperwork.

None of this makes a classic unstealable. It makes it harder to steal than the one parked next to it, which is almost always enough.

The storage side of that equation, and what a secure facility should actually offer, is a separate decision with its own trade-offs.