There are huge gaps in our knowledge of Shakespeare. We don't know where he was for much of his life, what he thought about the issues of the day, what his marriage was like, and much else besides.
Naturally, this means that there's a massive industry of Shakespeare scholarship and speculation, some rather more fanciful than others. Now, suddenly, the question of whether he was a Catholic has popped up yet again. There's a little evidence of possible Catholicism in the family, but no proof.
Just now, Radio 4 news breathlessly relayed the news that the signature of 'William, clerk of Stratford' (Gulielmus Clerkue Stratfordienses) has been found dated to his 'lost years', three times in the register of the English College in Rome, the priests' training college which churned out padres to sneak back into Britain and cater for the rebels in secret.
All very interesting, but hardly news: Hildegard Hammerschmidt-Hummel made this claim (in German) in 2006, and her book was translated in 2007. Why has this turned up now? Is the English College on a fundraising drive? I suspect so… Who knows whether this is true? Working out the bona fides of Shakespeare specialists is tricky, and Shakespeare provides a handy black hole into which people pour their obsessions.
More to the point: it's not definitely Shakespeare, and it doesn't add to our understanding of the plays. The Catholicism or not of Billy has been widely examined and the plays have been read in the light of this by many commentators. This story is more about the Shakespeare industry than it's about Shakespeare.