Conversation so far:
What was the name of the King to which Elizabeth of York was a niece?
Elizabeth of York was niece to King Richard III.
When did King Richard III die?
King Richard III of England died on 22 August 1485 at age 32.
Who took over as King of England after King Richard III's death?
Henry Tudor took the crown by right of conquest as Henry VII

Question: When did Henry take over?
Self-contained rewrite: When did Henry take over as the King of England?