This chain held five slaves. Part of it was bent towing a vehicle from the marsh.

When RAF Valley was extended in 1943, remarkable objects were discovered. William Owen Roberts was the Head Groundsman when a lorry became trapped in the mud. It was decided to tow the vehicle using an old chain found nearby. Later, Mr Roberts thought that there was something odd about the chain. He sketched it and sent it to the National Museum of Wales. The archaeologist Sir Cyril Fox was amazed and realised that the chain was about 2,000 years old. He travelled to Anglesey immediately and during the next four years over 150 Iron Age objects were discovered in Llyn Cerrig Bach.