Motorbike Tax disk location.

I read this story in MCN and thought it was interesting. The story goes:-
 

When I purchased a used bike it had the tax disk holder bolted inside the fairing so it could only be seen by looking down in front of the tank. I asked the dealer about this and he said it was ok and that some bikes even have their tax disks fitted inside the pannier!

Although I felt this was a more secure place for it to be, I wanted to check its legality and so I contacted the traffic police via their website and got an email back stating that, as long as the tax disk is fitted on the nearside of the bike, and I know where it is so that I can show it if asked, it is ok.

I always thought that a tax disk had to be visibly. Apparently not!!!