If you were retiring from a high-stress job before the age of 50, you'd probably be pretty happy too.

Especially if that job was prime minister of the U.K., and, you were responsible for a referendum where Britons voted to leave the E.U., wreaking havoc on the country's economy with no clear end in sight.

But maybe David Cameron could have done a better job of hiding his relief after announcing he would be replaced by a successor by Wednesday.

An instantly viral video making the rounds on Twitter shows the soon-to-be former PM walking away from the podium and into 10 Downing St. after making the announcement Monday. Unaware that his microphone is still on, he sings a lyricless little ditty ("doo doo doo doo") before stepping inside and saying, "Right. Good."

Wow, Cameron announces his resignation as prime minister, then walks back inside *singing* while still mic'd: <a href="https://t.co/wb4adNcCnk">pic.twitter.com/wb4adNcCnk</a> —@Yair_Rosenberg

Twitter users had a great time mocking Cameron's not-so-private celebratory tune.

<a href="https://twitter.com/BBCDanielS">@BBCDanielS</a> Sounds of a man who has just cleared his desk before a long holiday. —@156Sharknose

<a href="https://twitter.com/BBCDanielS">@BBCDanielS</a> Cameron reveals the secret "open sesame" tune to open the door of Number 10 —@thewyebird

Everything you need to know about Twitter: David Cameron on future of country - 16 retweets. Cameron humming after - Twitter meltdown —@BBCDanielS

Some speculated about what he was singing and what it meant.

<a href="https://twitter.com/bethanywhite">@bethanywhite</a> <a href="https://twitter.com/BBCDanielS">@BBCDanielS</a> It does sound like the ending bit of the West Wing theme tune. Oh dear Dave! —@BeckyMurphyEDP

<a href="https://twitter.com/OpperKop">@OpperKop</a> <a href="https://twitter.com/BBCDanielS">@BBCDanielS</a> was he humming the opening to the overture to Tannhäuser? Perhaps Cameron sees himself as the heroic minstrel-knight. —@MilesKing10

Cameron haters found the moment symbolic.

<a href="https://twitter.com/BBCDanielS">@BBCDanielS</a> Ah, he's humming doodoo - which is what he's left us in. —@amserinewid

<a href="https://twitter.com/BBCDanielS">@BBCDanielS</a> sums up his time in office. Just a bit of laugh, a man that has played at politics because he can. —@egalitarianfunk

A BBC journalist who posted the video on Twitter joked about its virality.

Everything you need to know about Twitter: David Cameron on future of country - 16 retweets. Cameron humming after - Twitter meltdown —@BBCDanielS

To be fair, Cameron isn't the first singing world leader we've seen. Maybe with those pipes, he could join the Van Cats.