The Kings Dyke brickworks, in Whittlesey, operated by Forterra, has operated continuously since its opening on June 24, 1969.
The brickworks was established by the London Brick Company and began by producing 1.25 million bricks per week.
Now Kings Dyke has four kilns and three chimneys – one of which is 400 metres tall and is one of the highest in Europe.
Andrew Mortlock, who is Kings Dyke’s resident London Brick Archivist and has worked on site for 45 years, said: “While the works has always been at the forefront of innovation, family and tradition have remained constant.
“Kings Dyke is unique for the fact it’s the only works still producing the original London Brick.”
London Brick is closely linked to economic regeneration due to its role in post-war housebuilding and is still mostly used for residential renovation, maintenance and improvement.
Stephen Harrison, chief executive of Forterra, said: “As we celebrate 50 years since the opening of Kings Dyke, we recognise the commitment of a great many of the site’s long-serving employees.”
Forterra will host a 50th anniversary celebration at Kings Dyke on June 26 from 6.30pm to 9pm that will feature talks from Mr Mortlock and Philip Parker, who runs Kings Dyke Nature Reserve on behalf of Forterra.
These will be a followed by a factory tour and a prize giveaway.
The event is open to Kings Dyke staff and a limited number of local residents on a first come first served basis via [email protected]