Can I fit a second lock on my door?

Yes, and it is one of the most useful reinforcements you can make to a door. The most common option is to fit a security deadbolt on the inner face, above the main lock.

With two separate locks, the door stands up much better to levering: the force is spread and there is no single point to give way. And whoever tries to get in has to beat two different locks.

Points to bear in mind:

• The deadbolt should have a security cylinder, not a basic one.
• The keep should be firmly fixed to the frame.
• The door should be thick and solid enough to hold it.

If you like, the two cylinders can be keyed alike so they open with the same key. It is very common in flats and bungalows in the area. It is all in security deadbolts.