On the accession of the Catholic Mary I to the throne, after the resolution of the succession crisis, Sadler lost most of his offices, including master of the great wardrobe, he was removed from the commissions of the peace and excluded from the Privy Council.
He was briefly under house arrest from 25 to 30 July 1553 before being granted a pardon on 6 October.
For the rest of Mary I's reign he did not sit in any parliament, remaining in semi-retirement at Standon, Hertfordshire.

During the reign of Elizabeth I, restored to royal favour, Sadler was sent to Scotland 8 August 1559 to arrange an alliance with the Scottish Protestants, and forward the cause of the Lords of the Congregation and Duke of Chatelherault.
 After the English became directly involved in the fighting at the Battle of Leith, he was one of the architects of the Treaty of Edinburgh.

In 1568 he was appointed Chancellor of the Duchy of Lancaster, and when Mary, Queen of Scots, fled to England, Sadler was unwillingly appointed to meet with the Scottish commissioners regarding that problem.
He was sent to arrest the Duke of Norfolk in Scotland in 1572 following the Rising of the Northern Earls.
He was reluctantly appointed jailer of Mary, Queen of Scots.
From summer 1584 to spring 1585, Mary was housed at Wingfield Manor  and Tutbury Castle, under Sadler's  charge.
During that time, Elizabeth was nervous about Mary's plans against her.
According to Andrea Clarke there was "a tangible, palpable sense of heightened levels of fear among Elizabeth’s government and ministers about her safety in the midst of the danger posed by Mary Queen of Scots, who for many Catholics was a figurehead".
Sadler was instructed to restrict Mary's freedom.
Francis Walsingham chided Sadler for taking Mary "hawkyng" and for giving her "more lybertye now then at any tyme when she was in the E of Shrewsbury chardge."
Sadler was required to post guards round the castle and to search the grounds "once or twice a moneth."
After the Babington Plot, Sadler was on the council that sentenced Mary to death.
On the accession of the Catholic Mary I to the throne, after the resolution of the succession crisis, Sadler lost most of his offices, including master of the great wardrobe, he was removed from the commissions of the peace and excluded from the Privy Council. He was briefly under house arrest from 25 to 30 July 1553 before being granted a pardon on 6 October. For the rest of Mary I's reign he did not sit in any parliament, remaining in semi-retirement at Standon, Hertfordshire.
During the reign of Elizabeth I, restored to royal favour, Sadler was sent to Scotland 8 August 1559 to arrange an alliance with the Scottish Protestants, and forward the cause of the Lords of the Congregation and Duke of Chatelherault.  After the English became directly involved in the fighting at the Battle of Leith, he was one of the architects of the Treaty of Edinburgh.
In 1568 he was appointed Chancellor of the Duchy of Lancaster, and when Mary, Queen of Scots, fled to England, Sadler was unwillingly appointed to meet with the Scottish commissioners regarding that problem. He was sent to arrest the Duke of Norfolk in Scotland in 1572 following the Rising of the Northern Earls. He was reluctantly appointed jailer of Mary, Queen of Scots. From summer 1584 to spring 1585, Mary was housed at Wingfield Manor  and Tutbury Castle, under Sadler's  charge. During that time, Elizabeth was nervous about Mary's plans against her. According to Andrea Clarke there was "a tangible, palpable sense of heightened levels of fear among Elizabeth’s government and ministers about her safety in the midst of the danger posed by Mary Queen of Scots, who for many Catholics was a figurehead". Sadler was instructed to restrict Mary's freedom. Francis Walsingham chided Sadler for taking Mary "hawkyng" and for giving her "more lybertye now then at any tyme when she was in the E of Shrewsbury chardge." Sadler was required to post guards round the castle and to search the grounds "once or twice a moneth." After the Babington Plot, Sadler was on the council that sentenced Mary to death.
Ralph Sadler