Complex sentence: On 23 May 1533 Archbishop Thomas Cranmer declared Henry VIII's marriage to his first Queen, Catherine of Aragon, a nullity, and on or about 25 January 1533 the King married the Dowager Duchess's step-granddaughter Anne Boleyn in a secret ceremony.
Split into simpler sentences: On 23 May 1533 Archbishop Thomas Cranmer declared Henry VIII's marriage to his first Queen, Catherine of Aragon, a nullity. On or about 25 January 1533 the King had already married the Dowager Duchess's step-granddaughter Anne Boleyn in a secret ceremony.