Essilor is the worlds largest manufacturer of spectacle lenses. Essilor has had a presence in Britain since 1881 when Société des Lunetiers opened its British operation in Hatton Garden, London. It maintained a presence in the city until 1975 when the company moved its offices and production facilities to Thornbury, near Bristol. The group employs 23,000 personnel world-wide, with around 400 people employed at Thornbury.