British Submarine technology is cutting edge, but for a century they have relied on one piece of technology to see above the water’s surface: the periscope.
In theory, the periscope is a very simple piece of tech which consists of two reflecting prisms or mirrors at 45° angles to one another.
The first deflects light down a vertical tube, whilst the second diverts the image so that it can be viewed, although more advanced technology allows for the image to be magnified.
Technology company Thales, formally Barr and Stroud, has been the sole provider of periscopes to the Royal Navy since the Victorian era.
In 1888, they were chosen to put a range finder into a periscope for the Royal Navy, which gave submarine's commander greater awareness of the battlespace at sea, whilst also helping with navigation.
In 1917, Thales became officially the sole supplier.
However, it was the simplest form of periscope that was used in WWI trenches to look over the top.
In WWII, periscopes were used in tanks so that the driver, gunner and commander might observe their surroundings, as well as for aim.
During the Second World War, Thales periscopes helped in the fight against German battleships like the Tirpitz, whilst the Cold War saw attack periscopes fitted to the Oberon class of submarines.
Gradually, however, things began to change. It was no longer periscopes that were wanted, but Optronic masts which Thales supplied on the Astute class of submarines.
Periscopes gave just one man, a sub's captain, a few seconds to risk a peek above the waves and form a picture of the battlespace.
Thales has just marked the century-long relationship with the Royal Navy with a special event, during which special ‘Apprentice Alumni’ panels were unveiled.
Harriet Baldwin MP, Minister for Defence Procurement, was present at the celebration. She said:
"It is a remarkable history that over 100 years we have been purchasing the periscopes for our submarines from these brilliant engineers here in Glasgow.
"Today is not just about celebrating that 100-year history, it's also about looking forward to the next generation and meeting some of the apprentices, some of the graduates who are joining the company."
Her Majesty's Naval Base Clyde is the future single home of the Royal Navy submarine service.
Thousands of apprentices have been through Thales in it's the last century. Some have put 50 years into the developing the niche engineering skills needed, but that hard won knowledge is being passed on to the latest Scottish graduates to arrive.
It thanks, in part, to Thales, that Britain has been able to stay ahead of the game when it comes to Naval Warfare.