One more thing.. and probably too late now, but I did use the Cho Pat dual action knee support for a week or so before, running 3 miles every other day and then used it on the day.
That combined with physio and sports masseur definitely enabled to run. It did present problems in itself though, pulled a little on the back of the knee - but I think on the day it prevented it from flaring up too much. Probably a little late to start messing around with now, but thought it worth a mention just in case.