The Octel Amlwch site was located to enable bromine to be extracted from sea water. This bromine was converted to dibromoethane (DBE) which was then transported to other sites in the company where it was used in the manufacture of leaded fuel anti knock compound. This page contains information about the rise and fall of leaded gasoline.
Early advert for leaded gasoline
The advantage of leaded gasoline
History of leaded petrol