 Poyer was a merchant and the mayor of Pembroke town in 1642, when he asked the local MP, Sir Hugh Owen of Orielton, for help in the defence of the county.He became Governor of Pembroke Castle and raised a force on behalf of Parliament, defending the castle against the Royalist commander, Richard Vaughan, 2nd Earl of Carbery.In March 1644 Poyer led a force that captured Carew Castle from the Royalists.