There's no car park for the Roaches. Instead, free lay-bys run for over half a mile along Roach Road below the crags, and the walk starts from the ones near Rockhall (ST13 8UA, but the postcode covers a wide area, so use the map directions above). Park only in the marked bays and don't block gates or driveways: wardens patrol every day, including bank holidays, and cars on the verges get tickets. It's often very busy, especially at weekends, so aim to arrive by about 9AM. When the lay-bys are full, the farm at the Roaches Tea Rooms sometimes opens a field for all-day parking for a small fee. There are no public toilets.

In the 1930s, Henry Courtney Brocklehurst of Swythamley Hall, a fellow of the Zoological Society of London, kept a private zoo on his family's estate, which then included the Roaches. Alongside yaks, llamas and nilgai antelope, he had a handful of Bennett's wallabies, a Tasmanian kind of red-necked wallaby, which came from Whipsnade Zoo.

During the Second World War the zoo had to be given up, and the animals were let loose on the moors. The yaks hung on for a while, and one lived on alone into the 1950s, but the wallabies did far better than anyone expected. Living on heather in winter and grass in summer, the colony grew to around 50 animals at its peak, and they were seen all over the Roaches, Back Forest and the woods around Lud's Church.

Life was hard for them, though. The bitter winter of 1962 to 1963 killed many, and 13 dead wallabies were found behind the wall of the wood at Rock Hall. Cars, dogs, falls from the crags and later hard winters took more. The zoologist Derek Yalden, who followed the colony for 40 years from 1969, recorded the last male dying in February 1996, and the last sign he found was a few droppings in 2009. People still report the odd sighting, but the wallabies of the Roaches are probably gone.

Lud's Church isn't a building at all. It's a narrow rift more than 100m long and about 18m deep, formed when a huge block of the Roaches Grit slid downhill towards the River Dane and left a gap behind it. Nobody knows exactly when it moved, but geologists think it was probably after the last ice age. Moss and ferns now cover the walls, and the chasm stays wet and cool even in high summer.

The name comes with a story. The Lollards, followers of the church reformer John Wycliffe, were persecuted for their beliefs, and in the early 1400s they are said to have met here in secret to worship. One of them, Walter de Lud-Auk (also written Ludank), is supposed to have been captured at a meeting, and the chasm may be named after him. A later version of the tale, written down by Philip Brocklehurst of nearby Swythamley in 1874, tells of a young woman called Alice who was fatally wounded when soldiers broke up a service. Around 1862 the Brocklehursts placed a ship's figurehead in a niche high above the chasm in her memory. Known as Lady Lud, it stayed there for the best part of a century before it fell and rotted away.

Lud's Church has also been linked to one of the great poems of the Middle Ages. Sir Gawain and the Green Knight was written in the dialect of the north-west Midlands, and in 1958 the scholar R. W. V. Elliott suggested in The Times that this chasm was the Green Chapel, where Gawain goes to face the Green Knight's axe. The poet Simon Armitage later said he thought it had to be the place. Local historians point out that there's no proof for either the Lollard story or the Green Chapel, but standing in the cold green gloom of the rift, it's easy to see why both legends stuck.