Elizabeth I's answer to Mary Queen of Scots was addressed to the man keeping Mary prisoner. It spoke of reconciliation. It also explained why Elizabeth would not yet write to Mary in her own hand.

On 31 October 1584, Elizabeth answered Mary's appeal in a letter to Sir Ralph Sadler, the English councillor supervising her captivity. Mary was at Wingfield Manor in Derbyshire. She had asked for the mistrust between them to be put aside. The reply gave Sadler something to convey to his royal charge, and instructions about how to convey it. It went to him because of a vow Elizabeth had made earlier, not to write to Mary "with our own hand".

Elizabeth was fifty-one. Mary was forty-one. Both descended from Henry VII: Elizabeth through his son Henry VIII, Mary through his daughter Margaret Tudor. The family connection gave Mary a claim to the English throne, and made her far more difficult to accommodate than an ordinary displaced relation. Elizabeth was Protestant and childless. Mary was Catholic, and Catholics who rejected Elizabeth's legitimacy could look to her instead. A reconciliation between these women would have to satisfy rather more people than the two women themselves.

They had once exchanged friendly letters and discussed meeting. No meeting had taken place. Their relationship had developed through written assurances, ambassadors and proposals, with each woman learning about the other through people who had interests of their own. The friendship Elizabeth's letter recalled had always depended on messages travelling between separate courts.

Then Mary lost her throne. Forced to abdicate in Scotland in 1567, she fled to England the following year seeking Elizabeth's help. Instead she was held in custody. Sixteen years later, she was still there. A woman who had been Queen of Scotland and Queen of France now needed permission to send her secretary to another woman's court.

Sadler's instructions, issued in August when he took charge, made the limits plain. Mary was not to ride far abroad. Exercise on foot or in a coach was to be taken near the house where she was lodged. Her keeper answered to Elizabeth for her security, and access to the world beyond her household was a matter of government business. A royal household could be maintained around her without giving her the freedom to leave it.

Mary nevertheless continued to negotiate. On 30 October, the day before Elizabeth's reply was dated, she wrote from Wingfield to Michel de Castelnau, the French ambassador in England. She pressed him to advance the proposed journey of her secretary, Claude Nau, and to speak of it on her behalf.

An envoy could carry what a letter could not.

Mary was working through the contacts available to her, trying to get a representative into the presence of those who could influence her future. Her appeal for reconciliation belonged to that effort, and she was pursuing it from a house she could not leave.

Elizabeth's response placed the responsibility for their estrangement firmly on Mary. Sadler was to tell her that she ought to have taken as much care to avoid giving cause for suspicion as she now took to complain of its consequences. The answer appealed to Mary's conscience and challenged her professions of innocence. The woman asking for reconciliation was being told that the mistrust was her own doing.

The letter then recalled what had been lost. Mary's friendship had once been, in its words, "a singular and extraordinary blessing of god". Now it was spoken of with regret, as something damaged. The language of a family quarrel sat inside an argument about responsibility and trust.

Yet the possibility of further negotiation remained. Elizabeth's goodwill had not been so completely extinguished that "no sparkes thereof remayn". She was prepared to hear what Mary proposed, and Nau was permitted to come to court. For a prisoner trying to secure a hearing, that permission mattered. It gave her someone who could go in her place.

The words also passed through Elizabeth's secretariat. Francis Walsingham, her principal secretary, had a hand in its warmer phrases. The message carried royal authority, but its warmth was written for a purpose. It could reach Mary without Elizabeth breaking the vow she had set upon their correspondence.

On the same date, Walsingham wrote separately to Sadler, enclosing the association pledge of the English nobility. Its signatories bound themselves to pursue to the death anyone on whose behalf an attempt was made against Elizabeth's life, and to bar that person from the succession. It did not need to name Mary. Sadler's papers held both kinds of message: language allowing reconciliation to be discussed, and a sworn promise aimed at the woman he was guarding.

For the moment, Mary had permission to send a man where she could not go herself. The talks brought no release. Elizabeth's answer survived among Sadler's papers, addressed to the keeper and meant for the captive, a cousin's message that had to pass through a jailer to reach her. The two women whose friendship it discussed never met.