Work started in October 1937, less than two years before the war. Seven great caverns were tunnelled under Brackla Hill for the storage of explosives, and above the caverns a reservoir was provided which is still in use today. Two housing estates for workers and their families were built at Bryntirion and Abergarw. Two huge hostels for 4,000 female workers were constructed at Island Farm and Pencoed. At Waterton there were over 1,000 buildings, including the Administration Building (now South Wales Police HQ).
At its height 32,000 people were working at the Arsenal, 75% of them women. They came every day by train and by bus from all over Glamorgan: there was a specially built railway station at the factory.
Most workers had no experience of factories or of ammunition – yet they had to work with volatile and dangerous materials. Bridgend was a Filling Factory: many millions of components were filled with explosives. Inevitably there were accidents; 22 people lost their lives, many were terribly injured. But for the vast majority, the social life, the friendships were enjoyable, even liberating. Women in particular earned wages that would have seemed impossible before the war.