I’ve linked to the announcement, above. It will bring you the tweet you see in the screenshot. Yes, a tweet is the government announcement.
According to the BBC report on the appointment:
[...] Prime Minister David Cameron made the announcement via Twitter.
Are formal (official?) government announcements on Twitter getting to be common practice? We do have an extremely high profile example to set the bar.
I don’t know Downing Street’s tactical goal with this tweeted announcement. But note that it’s a promoted tweet rather than simply a regular one.
Twitter describes promoted tweets as “ordinary Tweets purchased by advertisers who want to reach a wider group of users or to spark engagement from their existing followers.”
They are clearly labelled as Promoted when an advertiser is paying for their placement on Twitter. In every other respect, says Twitter, “Promoted Tweets act just like regular Tweets and can be retweeted, replied to, favorited and more.”
Obviously Cameron didn’t do the tweet himself (as neither did Obama in his official announcement re the US Presidential Election outcome). I imagine the goal isn’t direct engagement with the named tweeter, more a broadcast communication aimed at stimulating sharing – commenting, retweeting, etc.
Expect to see a lot more of this.