Info via an archaeologist friend: while these caves are "said to be used by the Knights Templar", they probably date from the late 18th century at the earliest and have nothing to do with the medieval order.
> One suggestion is that they were the result of quarrying during the 19th century, and were then turned by the landowners, the Legge family, into a grotto. It is alternatively speculated that the caverns are older, perhaps dating back at least to the 17th century, and some have associated them with the Knights Templar.
> The caverns are located beneath privately-owned woodland. Since at least the 1980s, they have sometimes been used for informal secret ceremonies and rituals, and vandalised, and were closed to the public in 2012 as a result. Later reopened, they were accessed by a photographer in 2017, and received widespread publicity.
https://historicengland.org.uk/listing/the-list/list-entry/1...
https://en.wikipedia.org/wiki/Caynton_Caves
> One suggestion is that they were the result of quarrying during the 19th century, and were then turned by the landowners, the Legge family, into a grotto. It is alternatively speculated that the caverns are older, perhaps dating back at least to the 17th century, and some have associated them with the Knights Templar.
> The caverns are located beneath privately-owned woodland. Since at least the 1980s, they have sometimes been used for informal secret ceremonies and rituals, and vandalised, and were closed to the public in 2012 as a result. Later reopened, they were accessed by a photographer in 2017, and received widespread publicity.