And I found this:
UK Drone Registration
To fly most drones outdoors in the UK, registering with the CAA is essential. Two requirements might apply:
Passing the DMARES theory test for a flyer ID if you'll fly.
Registering for an Operator ID and labelling drones with it if you're responsible for them.
Flying without these IDs is against the law. Registration is generally required, except for drones below 250g without a camera or considered toys. However, it's encouraged to obtain a Flyer ID even if not legally required, as it promotes safe flying.
The cost varies: Flyer ID is free for five years, while Operator ID costs £10 annually and is valid for one year.
For registration, children under 13 need a guardian's presence for a Flyer ID test, and one must be over 18 to register for an Operator ID. However, children under 14 can operate drones in both Open and Specific Categories.
Labelling your drone with the Operator ID is crucial. It must be visible, in block capitals taller than 3mm, secure, and placed on the main body of the aircraft.
