The cave consists of a number of interconnecting rifts, has 6 entrances and is often referred to simply as 'Flagpole' after the most commonly used of these. Traditionally, the Northern sections (Allotment Dig, Flagpole and Guano rifts) have been used to introduce many children to the underground (including myself). During 2018 & 2019 Grove Cliff Fissure and Rumble Chasm were connected providing longer, more sporting through trips. The most interesting of these is from Allotment Dig to either Grove Cliff Fissure or Rumble Chasm which will take the competent around 1.5 to 2 hours to complete.
Calcite is more or less non-existent in the caves however there is a good amount of moon milk in some areas. There are also many fossils which require a careful eye to spot the best examples.
Cave length: 590 m
Entrances:
Allotment Dig: SY 70347 72310 (50.5498, -2.41990)
Guano Rift: SY 70365 72269 (50.54943, -2.41963)
Flagpole Rift: SY 70367 72233 (50.54911, -2.41961)
Skittle Alley Rift: SY 70371 72217 (50.54896, -2.41955)
Grove Cliff Fissure: SY 70384 72172 (50.54856, -2.41936)
Rumble Chasm: SY 70380 72160 (50.54845, -2.41941)
Park in the cliff top road behind HMP Portland (the YOI) at The Grove. A few metres South of the ventilation tower it is possible to hop over the wall and follow a path Southwards. This is not the marked footpath which is found a few metres North of the ventilation tower. As you drop down through a small gully a few metres along the path, Allotment Dig entrance is seen up and to the right. The path can be followed downslope and around a corner. Just after a short climb up, the wide entrance to Guano Rift is seen. Continue along the path and around the next corner. The path splits. The steep climb up to the right leads into Flagpole Rift. Down and to the left, the path soon splits again. The slope upwards leads into the obvious corner and Skittle Alley Rift entrance.
Continue along the lower path for a further 60 m to find a man made, semicircular wall stretching the entire height of the cliff. Just before this is an obvious rift blocked at path level, the entrance to Grove Cliff Fissure can be found above by climbing 8m up onto a ledge. The climb is straight forward but exposed, very loose and earthy. A bolt has been placed halfway up to provide protection around the most awkward bit for the leader and a pair of bolts placed outside the entrance to arrange a belay / abseil. Those waiting below need to stand well out of the firing line of falling debris. If the cave is used more the climb should clean up, but for now care is needed.
The entrance to Rumble Chasm can be clearly seen on the far side of the above mentioned man-made wall 10 m above path level (i.e. just beyond the climb up to Grove Cliff Fissure). The climb up to the entrance is straight forward but exposed, loose and earthy. Two bolts have been placed just inside the entrance to arrange a belay / abseil, however the first up will need to do it unprotected.
Rather than attempt to describe the entire cave in one go, three through trips are outlined below which include details of side passages encountered on route.
More experienced parties may prefer the full Grove Cliff Caves experience which incorporates two of the three through trips mentioned above providing an opportunity to see pretty much all of the cave and enjoy abseiling down two pitches (both in daylight!).
Start by undertaking one of the longer through trip from Allotment dig to either Grove Cliff Fissure or Rumble Chasm, visiting all mentioned side passages on route to emerge on the under-cliff path. Then head North along the path and re-enter the cave via Flagpole Rift and undertake the Flagpole to Guano through trip. Once in Flagpole Rift, follow the description above until you have climbed up through boulders in Guano Rift. Two short, blind and entirely pointless passages (you can see the ends without entering) heading back into the cave are found at the higher level in the rift chamber. For the full experience rather than taking the obvious exit down slope, climb up boulders on the left hand side to arrive at a fine vantage point in daylight 12 m above the floor. Rig an abseil to finish (30 m rope for pull through). The bolts here can also be used for some SRT practice (topo below). A 25 m rope will suffice.
Trip time: approx. 2 h 30
A handline may prove useful for novices.
30 m rope, harnesses and descender if taking the pointless abseil exit from Guano Rift.
20 m rope to rig a pull through to descend from Grove Cliff Fissure entrance.
25 m rope to rig a pull through to descend from Rumble Chasm entrance.