Elaine, the anti-helmet joke is because TJ is anti-helmet and posts up endless stuff about how it isn't proven that helmets help and even that helmets make it worse – I think allegedly they make your neck twist and get damaged.
Be that as it may, for mountainbiking where you are not skidding along, but landing on uneven ground containing stones and assorted sharp, skull-penetrating objects, I reckon wear a lid.
Feeling much better now, had a glass or two of red wine and a quiet day.
I looked at the symptoms of concussion, yep, probably had mild. Interestly, the list does not contain 'displays urge to watch old episode of Minder and The Sweeney' – which is what I did when I got back yesterday after the crash… found it strangely soothing. HELP!