From reading Jimit's post below I get the feeling he parked at the first entrance to Dumpdon. Continue another 100m along Dumpdon Lane and there is an another entrance on the left (not that obvious until you get to it and assuming you're travelling north).
This splits in two, to the right is a farm track. To the left is a proper parking area with a small visitors board and the footpaths around Dumpdon Hill marked on a map.
If you go a short way up the farm track and through a field gate you can enter a field and from there walk across pasture up the steep hill to the northern entrance of the hillfort.
Of course this wasn't the route we took... but set off up the path from the car park and headed south, circling right around to the other side of the hill before we could find a way up. The path became indistinct at this point, but the side of the hill here had been recently mowed so it was possible to walk up and enter through another entrance into the hillfort.
As per Jimit's post, the views out aren't that good due to the southern end of the hillfort being planted with trees. The best outlook seemed to be from within the enclosure near to the triangulation point pillar.
EXTRACT FROM ENGLISH HERITAGE'S RECORD OF SCHEDULED MONUMENTS
MONUMENT: Dumpdon Camp
The monument includes Dumpdon Camp, a prehistoric hillfort located on a
detached hill, 260m high, at the southern end of a steep-sided ridge of Upper
Greensand between the River Otter and the Luppitt Brook. The flat topped and
triangular shaped hillfort of 2.6ha was defended by two substantial ramparts
and ditches on the northern side, controlling the only easy line of approach,
and by single ramparts on the east and west sides. A single inturned entrance
on the north east side provided the only known point of entry.
The layout of the defences largely reflects the configuration of the hilltop
which is flattest and widest towards its northern end, narrowing down to a
steep sided point at its southern end. The northern approach required the
strongest artificial protection and here the defences were bivallate with a
berm 30m wide separating two ramparts and their accompanying ditches. The
inner rampart is on average 1.3m in height on the interior with an average
width of 4.5m. It has a depth on the outer slope of 8.3m and is fronted by a
ditch which is mostly filled and waterlogged but which has an average width of
4.7m. The outer rampart is on average 1.2m in height and 3.1m in width. It is
fronted by a well defined ditch which has an average width of 3.5m and in
places is up to 1.35m deep. The remaining two sides of the monument were
defended along part of their length by a single rampart and a single ditch of
much smaller dimensions than those on the northern side and with a small
counterscarp bank on the outer side of the ditch. Controlled excavations have
demonstrated that the base of the eastern rampart was constructed of sizeable
chert blocks forming a wall 2.15m wide and 0.4m high; it was noted in the same
excavation report that the unexcavated western rampart becomes less distinct
and breaks up into a series of small dumps. It has been suggested by the
excavator, Professor Todd, that the defences were never completed and that
only the rampart base was constructed along part of the western and eastern
sides before work ceased. The fading out of the defensive ditch at about the
same place as the rampart base on both sides of the monument would support
this view. The hillfort was however provided with a single 20m long inturned
entrance close to the north east angle; this comprised a 7m wide causeway
flanked by low banks between the ditch ends. The thickened end of the southern
rampart may have been intended as a fighting platform covering the approach in
front of the gate. A gap in the northern defences is considered to be modern.
The interior of the hillfort is featureless and limited excavations in the
interior have revealed no signs of occupation. The suggestion is that Dumpdon
hillfort was neither finished nor fully occupied.
I was looking forward to visiting this site, it looks good on the map, it dominates the Northern side of the Honiton by-pass and A30 and is crowned by some noble trees.
What a disappointment! Parking is up a short,steep track with only room for a couple of cars and the NT sign baldly states its name with no other info.
Following a steep track up, I reached a flatter, semi-mown path which seems to encircle the lower slopes. Following this for a while and not getting any closer to the top, I struck off up hill through waist high bracken to be greeted by a wire mesh fence below the first, rather small, rampart. Scrambling over a broken bit and ducking and diving through the scrub and lower tree branches, I came to another fence on the second rampart. Following this I found a field gate which led to an open field with the Trig Point.
Where's the view? To the S. the scrub and smaller trees block any sight lines and to the N. and W. the way the hill slopes doesn't give any sense of this being a commanding defensive site. Somewhat miffed, I negotiated even more fences and scrambled back to the car.
Some sensitive scrub clearance and the removal of at least the lower fence (Does a farmer use the field for pasture?) could make this into a much more visitable site.
Of course one always has the awful thought that just round the next bend in the road is the proper access point with all the info one would need! Disabled: Drive-by, steep tracks and fences.
--It is, of course, a common practice in most places to make a neighbouring ancient object a kind of standard of age. At Honiton, and in the country round, "As old as Dump'n " used to be, and perhaps still is, a popular expression, the reference being to a British or Roman earthwork conspicuously visible on Dumpdon Hill, close by.
The National Trust are a bit coy about this site, so far no details are forthcoming. Perhaps others may have more luck. It looks impressive on the map and is most likely of Iron Age date. It is variously called "DumpTon" which is confusing.
Julian Cope mentions it on P183 of TMA.