M25 route

Ah yes, that makes sense. The train connection would also be better.

Ah yes, I've just realised that if we're going to follow the junctions in numerical order, we should go clockwise. I suppose it could be run in alternating directions like the Isle of Wight Randonnée, clockwise one year, counter-clockwise the next. Perhaps it should also start in Thurrock if counter-clockwise so that bridge services wouldn't have to funnel all the cyclists through in one go in the morning--not so much of a problem if clockwise, as people would be arriving at very different times.

I think one additional requirement should be for the route to include as few hills as possible, given that it's so long. From what TheCatMan was saying, that sounds achievable.

Chafford Hundred station (Lakeside/Thurrock) is served by C2C from Fenchurch St. as well. Although I am struggling for any pubs that I would be happy to leave a bike outside of! I guess, if the river crossing proved to be a massive hindrance you could go from Dartford and finish at Thurrock without using the crossing (I don't want to ditch the idea too soon though - the DRC website does indicate they can accomodate larger groups of cyclists with sufficient notice).

I think any major hills can be avoided - although there are some unavoidable hilly bits, notably in the south and south east . Probably another reason to run clockwise from Dartford - get them out of the way early.