Jay-Z and Kanye West invited a very special guest to join them on their 'Watch the Throne' tour stop in London Sunday night (May 20). Pop songbird Rihanna performed alongside the dynamic duo at their sold-out concert for two special tracks.

The singer wasn't scheduled on the bill, so this was a real treat for fans at the show. First, she joined Yeezy for a rendition of 'All of the Lights' from his Grammy-winning album 'My Beautiful Dark Twisted Fantasy.' Then she reappeared again to form an all-star trifecta for Jay-Z's 'Run This Town' from his 'Blueprint Vol. 3' album.

After the show, as we reported earlier, Ri-Ri partied with the boys at their lavish after-party and had a serious hangover the next day, which she regretted. “Interesting night! Sober and tired and bored," she tweeted.

Meanwhile, the Throne will wrap up their residency at London's O2 arena tonight (May 21) and Tuesday (May 22) before traveling to Switzerland on their European trek.

It's to safe to say that Rihanna conquered London with the kings of the Throne. The Roc is in the building!

Watch Rihanna Perform 'All of the Lights' with Kanye West

Watch Rihanna Perform 'Run This Town' with Jay-Z + Kanye West