Five Lever Deadlocks
Five lever deadlocks used to be the standard for external doors, however these days they have been greatly superseded by the latest and greatest British Standard 3621 kitemarked deadlocks. They are now generally considered by most to be the bare minimum level of security suitable for entry doors. Many insurance companies these days also require the BS3621 kitemark.
However they are still a very popular lock, particularly when replacing locks on porch doors etc, where you may already have a more secure lock in place on the main door, but would still like a decent level of security on the secondary door, too.
They are also still very popular in the countryside, where low-crime rates mean insurers often don't require BS3621 locks.