M25 is the ring road surrounding London. It has been dubbed "The World's largest Car Park" as traffic can be dismal around rush-hour times... On the other hand it is a great way to skirt London and if the truth be told, there are few places you will drive where the M25 does not prove to be part of the route.

I use it every day and have to say I have never had too much bother with it at all...

Mark (LHR)