There was one big surprise in the Chief Rabbi's measured letter on partnership minyanim last week.
Not the fact that he is against these services - he has made this clear before. And not that he confirmed that participation in a partnership minyan should not "preclude a person from assuming particular roles or responsibilities" in the United Synagogue. This was always US policy before it was upended in Borehamwood.
No, the surprise was the level of autonomy he was willing to give his local rabbis.
The rabbi of Borehamwood, Chaim Kanterovitz, was the Marah D'atra, or the halachic authority in his own community, and could manage his own "local considerations". In other words, Rabbi Mirvis seemed to be conceding permission to individual pulpit rabbis to set their own policy, even if it contradicts his own.
While a narrow reading of the Chief Rabbi's letter might apply this only to the question of partnership minyanim, his use of the phrase Marah D'atra - Aramaic for "Master of the House" - did seem to empower his rabbis more widely.
There has always been tension over who has the final say
Now, I realise that this might sound like a dry, technical detail of what has been a highly emotional debate. But it is actually key, both to understanding how this entire mess unfolded, and as a challenge facing the United Synagogue.
There has always been tension in the US over who has the final say in halachic matters. Pulpit rabbis, naturally, want as much freedom as possible to take their own decisions. They have their own qualifications, know their own communities, and want to be able to develop their own direction.
Yet, under a hierarchical organisation like the United Synagogue, they are answerable to the chief rabbi and are under his sole halachic authority. Rabbi Mirvis has not been so quick to give up this power when he really objected to a pulpit rabbi's decision. He certainly did not treat Rabbi Kanterovitz as Marah D'atra in 2014, when he wanted to allow the women of his community to read from a Torah scroll in front of other women, on Simchat Torah.
A real move towards more rabbinical autonomy would be positive. Our centralised system quashes our rabbis' initiative and creativity because the boundaries of what they can do are set relatively narrowly and tightly enforced. The development of our communities is hampered because no rabbi can be truly responsive to "local considerations".
Unfortunately, that was not what happened in Borehamwood. Reading between the lines, far from asserting more rabbinical autonomy, it looks like Rabbi Kanterovitz was simply replacing one rabbinic authority with another.
In April 2015, in a talk in Manchester available online, Rabbi Kanterovitz explained that he referred his questions about the halachic status of partnership minyanim to Rabbi Aharon Lichtenstein z'l, his former Rosh Yeshivah. He repeated this claim in his recent letter to his community, noting that he had also "consulted" the current Rosh Yeshivah - and then adding, by the by, that Rabbi Mirvis "is of the same opinion".
In America, the trend of yeshivah boys returning home from their gap year and continuing to consult their Rosh Yeshivah on halachic matters instead of going to their local rabbi has been noted for decades. It is still unusual, though, to see a rabbi employed by the United Synagogue openly take the same approach.
Given that almost all US rabbis are now trained in yeshivot abroad, and given the global village, we may be seeing more of this in the future. But it has far-reaching implications for the Anglo-Jewish rabbinate and for the chief rabbinate, further muddying the critical question: "Who's in charge?"
With so many rabbinic authorities in this marriage, it's getting a bit crowded.