Under normal employment law in the UK, work done for a company on company time is considered "work for hire" and the relevant IP belongs to that company.
That being the case why do employment contracts contain a clause repeating this?
For example:
"To the extent permitted by law, all rights in patents, copyright, registered design right, design right, trademarks or know how which may be created by you during the course of your employment ("Intellectual Property") will belong to XXXX absolutely. Any internet domain names registered by you in the course of your employment shall be registered in the name of XXXX. "
Is this strictly necessary? and if so why?