Although not Leith related. There are stories of similiar tunnels in Leith although they have never been confirmed-
“A local newspaper in the UK has revealed an elaborate network of secret tunnels and passages beneath Hertford, the ancient county town of Hertfordshire.
Local historians were aware of only one part of the network which was mapped in a document on public record dated 1898. The newspaper details numerous tunnels, many of which were blocked during the last century, and shows photographs of two other entrances. The existence, extent and purpose of the tunnels were leaked to a journalist by members of a mysterious secret society in the area said to be related to the Knights Templar and the Illuminati.
These revelations are restoring Hertfordshire to its rightful place in Templar legend, and literally put Hertford on the map in the Quest for the Holy Grail, and there is more to come” for more click here