-
It is a long day out, in Hertfordshire, meaning the views and bridleways start looking the same after a while. A friend was on MTB and bailed after 80km.. But you do you, perhaps you like entering that meditative state and counting wheat stalks along the way.. I'd say it's more enjoyable on a drop bar gravel/CX bike
If you were to shorten it, I'd look at cropping it around Ware/Hertford, with Broxbourne woods left as optional :)
All good things start at 6am :D
This is one of the nicest routes north of London I have in my list, perfected over the past 3y and rode less than a month ago, would recommend. 140km with 100km of offroad.
Stayer the Distance was a good collection of nice routes (the above shares some sections with a few of them).
Otherwise I'd recommend hopping on a train to Inverness and riding Badger Divide if you want a bit of bikepacking too
https://ridewithgps.com/routes/40167199