Commissario
Yes. Let's look at the page you linked.Are you even reading the official CAA guidance?
It's not a toy. A drone with a 4k camera is not a toy.
If it doesn't have a class mark then this applies:
below 250g - not a toy - with camera No Yes
If it's a class 0
C0 - not a toy - with camera No Yes
The bold 'Yes' are for Operator ID.
If an Operator ID is needed then the drone must be labelled accordingly (that's not mentioned on the CAA page). Note, I've not said the drone has to be registered anywhere, just that the appropriate ID is needed and the drone must be labelled.
Any other classes need both a Flyer and Operator ID.