Possible Clues:

• It ended in Britain with the Roman Conquest
• Irish one keeping silver for a time
• I get angry about working period
• Prehistoric era following the 'Bronze' period
• A region (anag) — period long ago
• Press silver badge at end of metalwork period
• Prehistory’s last period
• Early toolmaking time
• Post-Neolithic period
• A long time redeveloping a region