Every Harrow novel ends on the cliff path above the estuary mouth (sample). Last week I walked it in one go, from the old weather station to the sea.
It took six hours, with a stop for tea at the ferry steps. The path is narrower than it is in the books; I widened it for Ada, who walks it in the dark.
If you walk it, go east to west, so that the estuary opens up in front of you on the last mile.