From The Daily Mail. The article doesn’t really focus on The Musketeers, but does that mean it’s confirmed, then? It was posted very recently (~6 hours ago).
If this is true, damn. Sherlock and The Musketeers in the same month. BBC is spoiling me.
The Borgias, The White Queen, Da Vinci's Demons & casts
Now I refer the judgement of all my offences with my life and death wholly unto your most benign and merciful grace. To be considered by no justice of your majesties laws but only by your infinite goodness, pity, compassion and mercy. Without which I acknowledge myself worthy of most extreme punishment.”
— Katheryn Howard