On 21st June 1553, letters patent were issued changing Edward VI’s heir from his half-sister Mary to Lady Jane Grey, the eldest daughter of Edward’s cousin Frances Brandon, Duchess of Suffolk.
The following is taken from The chronicle of Queen Jane, and of two years of Queen Mary, and especially of the rebellion of Sir Thomas Wyat written by a resident in the Tower, edited by John Gough Nichols:
“Letters Patent for the Limitation of the Crown.
From the transcript of Ralph Starkey in the MS. Harl. 35, f. 364, which is preceded by this title : “A true coppi of the counterfet wille supposed to be the laste wille and testament of kinge Edwarde the Sixt, forged and published under the Great Scale of Englande by the confederacie of the dukes of Suffolke and Northumberlande, on the behalfe of the Lady Jane, eldest daughter to the said duke of Suffolke, and testefied with the handes of 101 of the cheife of the nobilliti and princepall men of note of this kingdome; dated the 21 day of June an. 1553;” and followed by this memorandum : “This is a true coppie of Edward the Sixte his will, taken out of the originall under the Greate Seale, which sir Robart Cotton delyvered to the kinges majestic the xij th of Apprill 1611, at Roystorne, to be canseled.””
Edward VI died on 6th July 1553 and Lady Jane Grey was proclaimed queen on 10th July. Jane’s reign was cut short when on 19th July 1553 Edward’s half-sister Mary was proclaimed queen and Jane was taken prisoner.