This animal is: real
Megabunus diadema is a small species of harvestman (Opiliones) found widely in Europe.
It has prominent spines atop its ocularium (the turret its eyes are on), the ‘diadema’ part of its name refers to this spikey crown (diadem). Its colours and spines act as camouflage, helping it blend in with lichens (and presumably make it hard for predators to swallow).
I see them quite regularly in woodland, resting with their legs stretched out flat on a gate post, or walking among mosses and lichens preying on small invertebrates.
External links:
Megabunus diadema on Wikipedia
Excellent photos of Megabunus diadema, by macro photographer Tim Jonas
You can look loads of cool pictures of Megabunus diadema on iNaturalist. Check out this one shedding its skin, and also this tiny young one.
This British Arachnological Society PDF pamphlet gives a nice introduction to UK harvestmen in general.
This Field Studies Council webpage has lots of harvestman information. To find Megabunus diadema, click ‘species’, then either enter the name in the search box or scroll down and click on it.
