Took my nephew back to London yesterday & to fix an issue with his canal boat, we went down the A1, A14, M11 then onto the North Circular, A406 Westbound, we came off at a junction, under the A406 & then North about a mile to N9 0AS.
He doesn't drive so knows very little about ULEZ, I'm a Northern foreigner in the place so know even less, however I have now found out that we did in fact go into the ULEZ zone & have been charged £12.50 for the privilege, however from what I can work out if you are traveling West on the A406 it's impossible to get off without incurring a charge.
In future I'll keep coming down the A1 & travel along the A406 East & not pay the charge as we won't have gone into the zone, the TFL website & phone lines are a waste of space, as neither can tell you IF your car was actually on camera, I feel like at least Dick Turpin had the decency to wear a mask.