Thrupe Lane Swallet

Thrupe Lane Swallet is a cave in the village of Croscombe, Somerset, on the southern edge of the Mendip Hills a few kilometres from Wells. It is a site for experienced cavers rather than a visitor attraction, and although its protected area covers only about half a hectare, it ranks among the most important vertical caves in southern England.

What is Thrupe Lane Swallet?

A swallet is a place where a stream sinks underground. Here the water disappears into limestone, runs through the cave and eventually re-emerges at St Andrew's Wells, the springs beside the Bishop's Palace in Wells. The cave reaches roughly 117 m in depth and has more than 1.4 km of surveyed passage. Almost everything in it is vertical: shafts and pitches formed along faults, joints and mineral veins.

The headline feature is Atlas Pot, a shaft about 60 m deep, the tallest single drop known in any Mendip cave. Cavers also cite the deepest water-carved (vadose) shaft in southern England.

Why is it protected?

The site has been a geological Site of Special Scientific Interest (SSSI) since 1992 and is part of the Geological Conservation Review. Its formation is linked to the Thrupe Fault, which runs east to west and brings Old Red Sandstone against Black Rock Limestone. For earth scientists it is a textbook case of a stream cutting deep shafts where different rocks meet.

Can you go in?

The entrance is gated and fitted with the standard regional lock. Keys are held by clubs belonging to the Council of Southern Caving Clubs (CSCC), and Mendip clubs with huts usually lend them to members of recognised caving organisations. Arrange a visit in advance. The CSCC access guide warns that the cave can flood suddenly and without warning.

You need single rope technique (SRT) equipment, experience on pitches, and a team that knows the cave or a local club to lead it. Anyone without those skills should choose one of the show caves nearby, such as Wookey Hole or Cheddar Gorge.

What else is nearby?

Croscombe lies on the road between Wells and Shepton Mallet. About 250 m to the east is Thrupe Swallet, whose stream flows toward this cave, and Hobnail Hole provides an alternative way in. In Wells itself, the cathedral, the Bishop's Palace and the springs where the underground route ends are all worth a visit.

When is the right time to go?

The cave responds quickly to rain, so conditions matter more than the calendar. After wet weather, or when groundwater is high, entering is dangerous. Pick a dry spell, check the forecast and ask the local club for current conditions.

Frequently asked questions

Is Thrupe Lane Swallet open to tourists? No. It is a locked cave for cavers who have arranged a key with a club.

How deep is it? About 117 m, with the largest shaft, Atlas Pot, around 60 m.

Where does the water come out? At St Andrew's Wells in Wells.

Is the site protected? Yes. It has been a geological SSSI since 1992 and belongs to the Geological Conservation Review.