Rode in 3:1 42×14. Probably a bit too big for proper Audax, hence the speed. You head for the crossing office and call the yellow phone and a van will take you across.
One point, the crossing is closed from 9:00 to 10:30. So leave too early and you’ll be waiting (as I had to).
The ride along the A25 is a road I know well and is pretty good. Thurock is awful, and the B road out is busy. Then you hit the Essex lanes and it’s lovely. Watford needs to be avoided. The original route is aiming for the A412. I will amend that. Possibly going outsite, although I’ve commuted to stevenage via Bushey a few times.
For Garmin, I originally wanted to follow the route on my 810. But route directions cause it to shut down? So I navigated using my 200 on breadcrumb trail, which was fine. Battery on the 200 lasted to Colnbrook, and I’m local from there. The 810 lasted even longer.
So my advice is take two garmins, navigate from a 500, use gears ;-). I’ll update the GPX from the proper start later.