Question: In what year was the last monarch under which Robert Waterton was a trusted servant of the House of Lancaster born?
Sentence (from "Henry VI of England"): Henry VI (6 December 1421 – 21 May 1471) was King of England from 1422 to 1461 and again from 1470 to 1471, and disputed King of France from 1422.
Relevant evidence: Yes