If Wikipedia is to be believed, it already has been used to prevent a Private Member's Bill from being debated relatively recently in 1999: https://en.wikipedia

If Wikipedia is to be believed, it already has been used to prevent a Private Member's Bill from being debated relatively recently in 1999: https://en.wikipedia.org/wiki/UK_parliamentary_approval_for_military_action https://en.wikipedia.org/wiki/UK_parliamentary_approval_for_... Also, I don't think this rule is really any more obscure than any of the other subtle details of the UK's unwritten constitution - people who care about this sort of thing almost certainly already knew about it (I certainly did!) The Guardian is probably trying to turn it into a big scandal because they don't really like the fact that we have a monarchy.