 His colleague on this occasion was Sir Arthur Mainwaring of Ightfield, another active local official whose family was to become almost as experienced in parliamentary representation as the Corbets, and a first cousin of Sir Andrew through his mother, Dorothy Corbet.Corbet was extremely active regionally in Elizabeth's reign.An important area of work was the Council in the Marches, from 1560 under the presidency of Sir Henry Sidney, the son-in-law of John Dudley, who was frequently involved in Irish affairs.