Before diving into the details you should know why we have copyright law and what does "Public Domain" mean.
Why do we have copyright law?
UK Copyright law is set out in the Copyright, Design and Patents Act (1988) and its amendments and exists to protect the intellectual standing and economic rights of creators and publishers.
UK Copyright protection:
- Is automatic upon creation of an original work.
- Covers the following types of works: original literary, typographical, dramatic, music or artistic, sound recordings, films and broadcasts.
- By default, rests with the author/creator of the work, but can be passed to others (e.g. employer/publisher) by contract.
- Generally lasts for the life of the author plus 70 years from the end of the calendar year in which the author dies.
What does "Public Domain" mean?
The term ‘public domain’ refers to creative works which are not protected by copyright. These works are owned by the public, rather than an individual creator or company, and can be freely used in any medium or format without having to obtain permission from anybody to do so.
Materials most commonly arrive in the public domain because the copyright on the work has expired (which in many countries, such as the UK, happens 70 years after the death of last known creator), or the creator has deliberately placed it within the public domain upon creation.
A Note:
It's important to keep in mind that copyright law is territorial, so different copyright rules apply in different countries. Works that are in the public domain in one jurisdiction are not necessarily in the public domain worldwide, so you should always pay close to attention to the rules of your own country.