I did this today, parking at Ongar Hill and walked to the Inner Trial Bank and back, and then around to the Ouse river and back.

With hindsight I should have started at the NW end of the walk by the lighthouse, as there was an uncut bit in the middle that was quite high grass with a few thistles thrown in for good measure.  Although the bit from the lighthouse is a bridleway (I saw a cyclist on it), so I opted for the footpath end as it'd be quieter.  I doubt it'd have been busy that end either though really.  If I do it again I'll try there instead.

All told, 11.3 mile walked, of which 11 mile was naked!   Only met one person the entire time, and that was on top of Inner Trial Bank itself (somewhat surprisingly).  It was hot, sunny, and early afternoon so not an ideal dog walking time.

Sadly I found the walk itself a bit boring though as it's pretty unchanging, plus there's no obvious circular route, but if you like wide expansive skies and the odd wetland bird, coupled with the delight of just being somewhere so remote, then maybe it ticks your boxes.  Lots of grassland butterflies too.