There’s some debate (at least in our family) as to whether Beech Bottom Dyke and this site were ever connected.
I enterpret Devil’s Dyke and the Slad are two sides of the same defensive enclosure *. Even from the Landranger you can see the contour lines following the existing ditches, and continuing around to the north and south where there is no longer a ditch. The lake to the south of the Slad is a definitely a continuation of the defences. If you look at the Slad on the ground this is really clear. Whatever Beech Bottom Dyke represents, I don’t think it ever connected with Devil’s Dyke and the Slad.
* Apparently I’m not alone here, as Sir Mortimer Wheeler was of the same opinion (you can’t argue with that, he’s a ‘sir’).