My mate came along with me to this one about 3 years ago, not signed up, on the off chance of running it and was comfortably able to sign up on the day. In fact there was a mass of tables and entry forms, so seemed well accepted.
With a 15,000 limit, and finishers in the last 3-4 years being 5-8,000 I don't see any reason why that can't happen this year!
It's probably worth a quick call to the organsiers who I'm sure won't say no.
I'd have been interested myself on a last minute decision but off to watch Man Utd instead!