We didn’t really know anything about this little mite, which is very numerous within the tops soil / detritus layer of the garden. But it turns out you can buy these mites on mass as a form of biological control for all sorts of things that feed on things people rather they didn’t.
Apparently its favourite food are Fungus Gnat larvae (but it will tackle thrips, springtails etc), which we think the following, filmed from soil taken from our garden, may well be.
…and here’s the little fella himself. Very quick little creature, likely disturbed by the bright light of the scope. Seemed little interested in attacking any of his fellow soil mates.