Chesten Marchant

Chesten Marchant or Cheston Marchant, who died in 1676 at Gwithian, Cornwall, reportedly having reached the age of 164 (the claim apparently going back to either William Scawen or, according to Henry Jenner, to William Borlase), is believed to have been the last monoglot Cornish speaker, as opposed to other speakers such as Dolly Pentreath who could also speak English.