Tom Griffin (London, The Green Ribbon) The Telegraph's Damian Thompson has a theory about why Gordon Brown is considering ditching the Act of Settlement.

This is the first time for decades that Catholics in Scotland – traditionally the most loyal of Labour voters – have been faced with a Protestant Scottish PM who cannot hide his contempt for aspects of Catholic teaching. Meanwhile, the Scottish Nationalists are working hard to ditch their anti-Papist prejudices. Alex Salmond is on the most cordial terms with Cardinal O’Brien.

I'm not convinced there's any particular Catholic antipathy to Brown, but there is something in this.

Salmond has been a vocal campaigner for repeal of the Act, while Cardinal O'Brien has declared himself "happy that, if it is the wish of the people, Scotland becomes an independent country."

This rapprochement may have as much to do with ethnicity as with religion. Many Scottish Catholics are of Irish origin, (O'Brien himself is from Co. Antrim), and the SNP has increasingly embraced Ireland as a model for Scottish independence.

These developments won't deliver O'Brien's co-religionists en masse to the SNP, but they may contribute to the ongoing breakdown of the old sectarian voting patterns.

That in itself could have significant implications for Labour and for the union.