To strip his brother of his titles and to evict him from his home is the most consequential action King Charles has taken since he ascended the throne in 2022.

The defenestration of Prince Andrew, now to be known only as Andrew Mountbatten Windsor, and the removal of his cherished privilege of royal status is an act of utmost ruthlessness by a king. Ascending to the throne at the age of 73, Charles always knew he would play a caretaker role for the monarchy and so could not allow rot to set into an institution that lives and dies by public consent.

The damage that Andrew’s association with Jeffrey Epstein and Ghislaine Maxwell continued to inflict on the reputation of the royal family was simply too much for the king not to act as he did on Thursday evening. Charles has been described by his biographer Catherine Mayer as “loyal to a fault. Sometimes to the point of fault,” but this was too much.

The queen’s longevity always meant that Charles’s reign would be relatively short and therefore one of his most important tasks would be to bequeath the institution to Prince William in reasonable repair. William is relatively popular with the public and to leave him with a festering crisis for the sake of the feelings of his younger brother, recently caught lying about his continued association with Epstein, made no sense.

It emerged earlier this month that Andrew had emailed Epstein in 2011 after a picture of him with his arm around the teenager Virginia Giuffre, who he is accused of having sex with, was published in 2011. He previously claimed he had cut off contact with the sex offender by this point, but instead he is alleged to have told Epstein that “we are in this together”.

Then when the BBC this week reminded the world of a picture taken in the garden of Royal Lodge, the Windsor home Andrew is being turfed out of, which featured not only Epstein and Maxwell, both convicted child sex offenders, but also the convicted rapist Harvey Weinstein, it cannot have been difficult to decide to deliver the final blow. Charles decided that neither he nor the institution of the royal family could be “in this together” ever again with Andrew.

But this was not just the action of the chief executive of an institution sometimes called “the firm”. This was a family matter and therefore emotionally charged. The queen is said to have doted on Andrew and his astonishing self-assurance has been attributed by some to that mothering by the queen who is said to not have offered the same indulgences to her older children. Charles would no doubt have had his late mother’s views in mind when he signed off Thursday night’s statement announcing the “formal process to remove the Style, Titles and Honours of Prince Andrew”, that “notice has now been served to surrender the lease” on Royal Lodge and that “these censures are deemed necessary, notwithstanding the fact that he continues to deny the allegations against him”.

In the simplest terms the issue also seemed to boil down to a question of whose side are you on.

As the final line of the statement from Buckingham Palace read: “Their Majesties wish to make clear that their thoughts and utmost sympathies have been, and will remain with, the victims and survivors of any and all forms of abuse.”