The APK requirement is that tires must have a minimum 1,6 mm tread depth, and no drought cracks where the carcass is visible.
While the flank of the tire can look like a dried-out clay soil
But it can happen that tires are even older than 10 years and show the necessary drought cracks. Without the carcass visible. That is not an MOT rejection, but it is very dangerous. The tires are then structurally outdated.
The maximum recommended age for tires is set at 6 years.
A nice Dutch-language magazine which has a broad insight especially when it comes to cars, and also gives very useful addresses for when you are busy with a restoration. Engines are also welcome in this magazine, but the main thing is the coaches.