Unless you’ve spent most of the day trapped under something heavy, you’ve probably heard that the Duchess of Cambridge is in labour. Catherine and William arrived at St Mary’s Hospital in Paddington, west London, at 6am GMT this morning, and the royal push is now well underway.

The couple have not announced the sex of the baby-to-be, but that hasn’t stopped Twitter speculating. Indeed, mentions of the royal baby have reached such a fever pitch over the past 24 hours that they’re even outpacing tweets sent to the micro-blogging social network’s reigning l’enfant terrible, Justin Bieber.

Tweets mentioning the #RoyalBaby hashtag, which currently sits atop Twitter trends in the UK, have leapfrogged all replies sent to @JustinBieber, as seen in the Topsy chart below.

A couple of caveats here. One, Topsy only tracks tweets that “matter”, which it defines as those that have been retweeted or contain a link, which is going to dilute the totals on either side. And, two, while use of the #RoyalBaby hashtag is only going to mount once the babe is born (the data above is lagging), it will be interesting to see if it can topple Bieber’s July 15th performance. Because, let’s face it, otherwise he’s having kind of a quiet week, and that’s perhaps the only reason why he’s (currently) in second place.