Perhaps the single biggest reason for the drop in thefts of newer cars in recent years is the standard fitting of alarms and immobilisers to all new vehicles. Alarms are an effective deterrent to both car theft and theft from your vehicle, and electronic engine immobilisers are highly effective as they prevent the engine from actually starting.

In combination, they are enough to put most car thieves off, and nowadays you can even fit combined alarm and engine immobilising systems to older cars as well.

The Motor Insurance Repair Research Centre (MIRRC), also known as Thatcham, has been testing and approving vehicle security systems since 1992. It publishes a list of approved products and systems, and recommends a category one system which includes it switching on automatically when you leave the car, an 'anti-scan' key-code system and a battery backed-up siren.

If you already have an alarm but no immobiliser, don't worry. Engine immobilisers can also be fitted on their own and your alarm can be upgraded to 'category one' if it doesn't already meet the Thatcham criteria.

Whilst fitting a Thatcham approved system doesn't guarantee that your car won't be stolen, it will considerably reduce the risk. For details of approved systems call the Vehicle Security National Helpline on 0870 550 2006.

It is also important that alarm and engine immobilising systems are fitted properly to your car. The AA recommends installation by a Vehicle Systems Installation Board (VSIB) approved installer. Expect to pay around £120 for an engine immobiliser and more for a combined system.

If you already have one or more security device, or you are thinking of securing an older model vehicle, it is worth checking your car security rating to see if you meet the necessary standard.