This rumour is based around a pirate/privateer/captain Crow who was supposed to have had smugglers tunnels leading to the river.
R S Clare is one of the oldest companies (over 250 yrs) in the area and is based at Stanhope street but there is a Crow street which crosses the site (it's been closed off by the company for many years)
The site is supposed to have been used previously by Crow.
I first heard this in the 1970's, but not a thing since. Nice rumour though.