Although she was marginally implicated in her father's attempt to place Lady Jane Grey on the English throne and affected by his attainder, Mary Dudley was one of Queen Elizabeth's most intimate confidantes during the early years of her reign.

Still one of Elizabeth's favourite ladies, Mary Dudley retired from court life in 1579, suffering from ill health during her last years.

[1] Four months later Henry Sidney became Chief Gentleman of Edward VI's Privy Chamber;[4] he was knighted by the young King on the day his father-in-law, who headed the government, was raised to the dukedom of Northumberland.

[6] According to Lady Jane it was Mary Dudley who, on 9 July 1553, called upon her to bring her to Syon House, the place where she was informed she was Queen of England according to King Edward's will.

[1] In early 1554 he went with an embassy to Spain to plead with England's prospective king consort, Philip, for the pardon of his brothers-in-law John, Ambrose, Robert, and Henry.

[8] John Dudley, the eldest brother, died days after his release in October 1554 at Penshurst Place in Kent, the Sidneys' manor house granted to them by Edward VI in 1552.

On Elizabeth I's accession in November 1558 Mary Dudley became a Gentlewoman of the Privy Chamber "without wages", an unsalaried position which left her dependent on her husband.

[16] In the 1559 negotiations over Archduke Charles, the Habsburg candidate for Elizabeth's hand, she acted as go-between for the Queen and her own brother in their dealings with the Spanish ambassador Álvaro de la Quadra and his Imperial colleague, Caspar von Brüner.

[18] Yet Elizabeth cooled down again and gave Mary Dudley further instructions to deal with the Spaniards, until she herself told de la Quadra "that someone had [spoken to him] with good intentions, but without any commission from her".

[27] The same castle was the scene of the great festival of 1575, at which the whole Sidney family were guests and Mary Dudley excelled in stag hunting.

[1] By the 1570s, Sir Henry Sidney and his wife had become somewhat disillusioned and embittered about lacking financial rewards on the Queen's part for their long service.

[1] In 1572 Mary Dudley even had to decline a barony for her husband in a letter to William Cecil, himself Baron Burghley since the previous year:[29] The expenses such a title implied were simply too great, Sir Henry's mind being "dismayed [by the] hard choice" between choosing financial ruin and royal displeasure "in refusing it".

[31] All in all though, she explained, "old Lord Harry and his old Moll" would accept "like good friends the small portion allotted our long service in court; which as little as it is, seems something too much.

"[1] Elizabeth was still attached to her old friend when Mary Dudley left the court in July 1579—because of bad health,[1] or out of solidarity with her brother Robert, Earl of Leicester, who was in disgrace for having married.