Welcome to KEEPING WATCH - a fortnightly podcast for anyone and everyone interested in lighthouses, lighthouse keepers, light vessels and other aids to maritime navigation. 

KEEPING WATCH is brought to you in association with the ALK - The Association of Lighthouse Keepers - a charitable trust in the UK dedicated to keeping lighthouse heritage alive. 

We’ll hear from former lighthouse keepers, authors of books about lighthouses, people born and brought up in lighthouses, archivists, historians and many others interested in lighthouses, their construction, history and service.

This week we turn our attention to Belfast, and specifically to the Titanic Quarter. I want you to picture a vast glass cylinder, right on the waterfront, a bit like a lighthouse lantern room. Inside is one of the largest lighthouse optics in the world, weighing 10 tonnes and measuring 7 metres tall. 

I’m talking about the Great Light - which opened to the public in 2018 and is now one of Belfast’s iconic monuments. The huge Fresnel Hyper-Radial lenses of the Great Light were the largest lenses ever made in the world - and came from the lighthouse on Mew Island, following modernisation by the Commissioner of Irish Lights. 

But the optic’s lenses were originally built not for the Mew Island light, but for the lighthouse on Tory Island on the opposite coast. In its original form, the Tory Island optic comprised 18 lenses, with three tiers of six lenses. 

It was not until the 1920s that this vast optic was split, creating two separate optics, one to return to Tory Island, and the other for Mew Island. 

How do we know all this? It’s pretty much all thanks to the tireless research of one person, Dr Sally Montgomery, who is now on the board of the commissioner of Irish Lights. 

I was lucky enough to meet up with her online last week, and she told me that the project started with a letter, in 2015, from the commissioner of Irish Lights. Could the Titanic Foundation find a new home for the Fresnel Hyper-Radial lenses from Mew Island. 

Dr Montgomery soon discovered that parts of the chronology and recounted history of the optic didn’t make sense - and so began more than two years of painstaking research to establish an accurate account of when and where the fresnel lenses were made, and how they came to serve two lighthouses. 

It’s a remarkable story - and I hope you enjoy it.  

Find out more about The Great Light: https://www.greatlighttq.org

Read Dr Montgomery's own account of The Great Light research and rehoming: https://www.greatlighttq.org/about/history/the-great-light-unravelling-its-past/

Her book recommendation: A Short Bright Flash, by Theresa Levitt

Visit the Association of Lighthouse Keepers: www.alk.org.uk