Thousands of eager pop fans are soaking up the sun as Radio One's Big Weekend kicks off in Londonderry.
Artists including A$AP Rocky and Dizzee Rascal took to the stage this afternoon as the three-day event began in Derry's Ebrington Square.
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But to add to the already heaving line-up of pop acts, Robbie Williams joined Dizzee on stage - much to the delight of the some 12,000 fans that turned up.
A host of acts soon followed the big-name surprise guest, with Katy B taking to the 1Xtra Arena this evening among others.
Set to headline is Scottish DJ and producer Calvin Harris tweeted his fans earlier this afternoon - pictured alongside girlfriend Rita Ora en route to the gig.
But disruptions at Heathrow airport earlier today due to an emergency landing forced several artists to pull out of the show.
A statement from the Radio One press office said:
"Unfortunately due to the travel disruption affecting Heathrow we've had to cancel a few performances but we've still got an exciting line-up for our audiences."
The event is due to finish around midnight this evening.
Biffy Clyro will headline the Main Stage on Saturday night while Bruno Mars will close the show on Sunday.
Dizzee Rascale & Robbie Williams - Going Crazy
Rita Ora – Radioactive
Rudimental – Waiting All Night (feat. Ella Eyre)
J Cole – Power Trip