I am indebted to one of our readers for telling me about this.
It seems that our native hedgehog population is declining and one reason for this is that they are not able to roam around due to secure fences and walls stopping them.
The best way to help is to cut small 13cm x 13 cm holes in the bottoms of our fences to allow them to roam freely. You can flag up to tenants what the hole is for by putting the little hedgehog highway notice above it (maybe also mention it in your tenants pack).
Find out all about it from this WildlifeWatchUk video (the pdf they refer to is here). Another useful site is Hedgehog Street which has links to places where you can buy the notices.
A problem in cutting holes arises if there are concrete (as distinct from wood) gravel boards along the bottom of the fence where it meets the ground.
I still have concrete gravel boards put in because I feel they last better than wood. But since I learned about the importance for wildlife of having a hedgehog hole I specify that each gravel board is cut short before it is installed in order to form a hedgehog hole.