Ariana Grande has pulled out of a surprise performance at tonight's Brit Awards hours before she was due to appear on stage. Kevin Winter / Getty Images A source with knowledge of the situation told BuzzFeed that Ariana had been taken ill and despite wanting to proceed with the appearance, was advised by a doctor not to fly to the UK. View this photo on Instagram instagram.com Ariana had been scheduled to make a surprise appearance at the ceremony to perform a tribute to the victims of the terrorist attack at her Manchester concert last May. PA The attack killed 19 of her fans and she returned to the city to organise a benefit concert for the victims' families just two weeks later. Brits organisers were hoping that the Ariana's surprise performance at the event would be "the talking point of the night." It's now reported that Liam Gallagher has stepped in to fill Ariana's slot. Within minutes of the news breaking, fans took to Twitter to express their sadness that Ariana wouldn't be performing and wished her better. freya @freyalinesss the fact that @ArianaGrande was going to do a surprise performance at the #BRITs2018 for the Manchester attack melts my heart 💔 :( 05:08 PM - 21 Feb 2018 Reply Retweet Favorite beri 🌙 @deeplybutera @ArianaGrande we love you so much, i hope you're alright get well soon. 💞 05:08 PM - 21 Feb 2018 Reply Retweet Favorite Chantel @skyhighbutera @ArianaGrande really hope ur okay! we all love you and are always here 💗 05:06 PM - 21 Feb 2018 Reply Retweet Favorite A spokesperson for Ariana declined to comment when contacted by BuzzFeed.