According to one leading UK insurance company, there could be as many as 20,000 squatters in the UK and, while this largely relates to residential property, commercial premises are by no means exempt.

If you assume that there is an average of four squatters per location, this means that up to 5,000 landlords could be suffering damage to their rental property, a dramatic reduction in its market value and a loss of rent .

There are forms of property owners' insurance that can be taken out to cover the risks involved, but on the basis that 'prevention is better than cure' landlords should be taking steps to reduce the risk. This falls into two areas; protecting your rental property physically and having the right landlords' insurance protection.

The first line of defence for any owner of unoccupied property is to ensure that the premises are secured against casual unauthorised access. Open windows are an invitation to burglars and squatters, as are doors with keys left on the inside, near windows that can easily be broken and an arm thrust through. However much you may wish to ensure that your property is ventilated while unoccupied, leaving a window open is not advisable. Even locking a window open is inadvisable, because few window locks are strong enough to withstand even a light assault. On the other hand, locking windows closed is a good idea, because this makes breaking in far more difficult.

Doors should, of course, be well protected. Simple rim-latches represent no defence against the lightest assault; there are several high quality versions available but, in general, a five-lever mortice deadlock is far better.