Back home I tryed to identify it but without success. My insect literature was not up to the task so I posted it on a Danish website called Fugle og Natur (Bird and Nature) where all sorts of experts help people identify all sort of things. Within a couple of hours a Norwegian beetle expert came back with an answer. The species was Mycetophagus fulvicollis, and it was, as he said "quite rare". That was fun, I thought, and entered my observation into a Danish database, where all kinds of sightings are held for researchers, and environmental organisations and so forth can study them at their leasure.
Now quite rare is fine by me, but just how rare my beetles were I didn't realize until a few days ago when I suddenly received an email requesting more information about my observation. Apparently someone had stumbled upon my sighting and had done a double take, or perhaps had fallen over in a faint. It turns out that Mycetophagus fulvicollis was declared extinct in Denmark in 1997. Quite rare, indeed!