Offa's Dyke damage claims: Police investigate 19 August 2013 Last updated at 17:21 Police say an investigation is now under way after reports a large section of Offa's Dyke ancient earthwork was damaged near Wrexham. North Wales Police confirmed it had been passed information by Welsh government historic environment service Cadw. The protected 1,200-year-old monument, built in the 8th Century, appears to have been excavated on land near Chirk. Cadw said it was too soon to say whether the dyke could be repaired. A spokesman for the Welsh government said information was handed to North Wales Police on Monday. It is thought that King Offa of Mercia built it as a boundary between his domain and Wales.