We finally removed the heating mat from under this hive. They definitely don't need it any more!
A nice hive, the red queen is still there, tons of brood, pollen and some drone larvae but no varroa. Added a box on top to make some space.
This hive is not in a great place though: there is a red ant highway right through the middle and there are a lot of plants growing up around it. Too late to move it now though.