Andrew's point about the difference between GPX files which are created from the (online) map (whether or not aided by paper route guides) and as tracked on the ground, with or without amendments to resolve detours (or just errors), is a good one. It would help enormously if downloadable GPXs were both labelled ('as mapped' or 'as tracked') and dated.

Having nearly completed a version of the Trans Pennine Trail - an easy but long route-set (almost 300 miles) on mainly bike trails, canal towpaths and sometimes minor roads, but with many walker-only variants plus occasional diversions of my own - aided by the GPX track file in the LDWA database, I now have an 'as tracked' version which differs from the one downloaded. I don't want to replace the downloadable version, just add mine to it.

Iain

So having walked the complete London Loop having armed myself with the GPX file from the Long distance paths database, maps and TFL route descriptions.
I mostly followed the way marks on the ground but used the map/GPX and route description where the way marks were missing or unclear/tampered with.
I found that GPX from the Long distance paths database as inaccurate/wrong in places because it looks like it was just drawn from the green diamonds on the 1:25000 ordnance survey map.

So I have joined up the GPS traces of me walking the route (removing start start/finish point detours) and created a route focusing on where there were key route decisions to make.

This is available at https://my.viewranger.com/route/details/MjEwMzkyMQ==
and I have sent an offer of providing this as a GPX file to be included in the database