Hard run

Went for a 2hrs 15min run today through Hyde Park, Green park St James park, over westminister and all the way over to and around Battersea park and then up via Sloan square back into Hyde park and home. The run was a lot harder than the other weeks. Think I was wearing too many clothes and waited too long after breakfast so didn't feel that full of energy. Plus my knees were taking a toll as well. Was pretty painful towards the end and it got me really worried.
Starting to doubt that I'll be able to run it under 4 hours and I suppose is ok, I did after all miss a months training due to illness, but if me knees are hurting this much after about 23.5km, what are they going to feel like after 42km?!
Feeling a little bit down...and scared. Today's run wasn't fun after 1hrs 45min so I'm starting to get worried about how I'll feel during the actual run. I know there will be lots of supporters there, but still. Tiredness I can cope with but when I feel my body is giving in... that worries me.

Time to put ice on my knees and try to keep the pain away :(