How far was Mary, Queen of Scots, a threat to Elizabeth's throne?

Mary played an essential, iconic role for Catholics revolting, giving them a specific aim – to see her crowned. ‘The Ridolfi plot’ in 1571 showed continuity in Mary’s conspiracy, as once again she was aligned to the Duke of Norfolk, and also – rather worryingly – the Spanish. In the period of foreign tensions, and following English excommunication, Elizabeth feared executing Mary, and instead utilised law to limit religious opposition and her political skill to put-down the Catholic revolts without creating martyrs. The Bond of Association in 1584 showed Elizabeth’s subtle anti-Catholic legislation, while the thwarting of the Throckmorton plot – without executing Mary, demonstrated Elizabeth’s sharp political insight, which rendered Mary little threat. Elizabeth only issued warrant for Mary’s execution when she had sufficient evidence, gained with the help of Walsingham, to prove that Mary conspired to kill her – thus demonstrating her skilful application of treason law.

Mary’s threat to the British crown has been surmised by contemporaries:

Mary had a little lamb, its fleece as white as snow,

And everywhere that Mary went, the little lamb would go.

The ‘fleece as white as snow’ is indicative of how Mary’s followers; the Spanish and English Catholics alike were strictly supporting Mary as the single individual renown for her Catholic sentiments, making her the only realistic potential Catholic successor. Her threat was not so much personal, as an amalgamation of people and their religious grievances – many of which had existed since the reign of Henry VIII, leaning on her as a figurehead. However, without her, the majority of Elizabethan rebellions would never have come to fruition, as her principle threat to the throne was her presence as a potential successor. It is thus debatable that had she led her ‘lamb’ more opportunistically and directly, she may have spurred a flock of unsettled Catholics into opposition of the crown, and had success in overthrowing Elizabeth. Though, as she was, making only reactionary efforts to support other initiatives, she wasted the potential influence she held and played into the hands of a superior Elizabeth, and leading her ‘lambs’ to the slaughter.