Update: Another reader e-mails:

Regarding this e-mail from your correspondent:
’This institute makes no claim to be “Catholic”, as its website makes clear. In fact, very few of the articles it produces are written by Catholics. Lord Acton was, of course, not a Catholic and his ideology was typical mid-19th century liberalism. ’
Leaving aside the issue of the Institute, Lord Acton was, in fact, a Roman Catholic (though without ultramontane sympathies), wasn’t he?

The answer is yes. Catholics can be classical liberals, too — which is how I can make the mistake in identification.