Theory:pre-illness
I have this theory, or is it a hypothesis, it goes like this:
This morning I woke up feeling mildly conscious that I may or may not have a cold coming on. Yesterday I had bags of energy, I chopped down a tree at 7 in the morning & thought the Lumberjack song. So is there a link?
Not with the song but having loads of energy before getting a cold. There are a few times that this has been noticable pre-illness in the past.
I rode 56 miles today, the route outwards was fine, but the return was tortuously slow. Now my tiredness matches a 70 mile ride so that nervous feeling of pre-cold has cost me 20 miles. 
Later:Shopping
Remember my rant about Trust computer peripherals?: Well I found an online supplier that deals in Nisis replacement pens, they are identical apart from the colour. Ordered one replacement pen.
Micycle 