With the kind of money involved in staging large concerts and world tours, and the potential disappointment to fans, cancelling a show is a decision no performer takes lightly.
DJ Khaled pulling out of Wireless this month was a blow to fans, especially as the cited reason of "travel issues" initially seemed at odd with an image he'd posted on Instagram the day before complete with the caption, "Still on vacation!!!!!!!!" Drake stepped in as a replacement, and Wireless later explained that they'd known "for a few months" that Khaled couldn't make it, but they'd "tried to make it work".
And that's far from the strangest set of circumstances that have led to a much-loved performer cancelling a scheduled appearance...
1. Wishing the Dalai Lama a happy birthday
Maroon 5 had been booked to play two shows in Shanghai and Beijing in 2015, but found that both concerts had been cancelled suddenly, with no clear reason as to why. On further investigation, a (since deleted) tweet by the band's keyboard player Jesse Carmichael appears to have angered both Chinese fans and the authorities, after he said that he "sang happy birthday to his holiness" the Dalai Lama.
This was interpreted as a political act, as the religious leader has been exiled from his native Tibet since 1959. And it's not the first time musicians have found their invites to perform in China rescinded on similar grounds. Noel Gallagher and Linkin Park both had prospective Chinese concerts cancelled after showing their support for the Free Tibet movement.
2. Pigeon strike
A large venue, of the sort that plays host to rock concerts, is apparently a haven for pigeons, who will often roost in the upper scaffolding, and then fly around while the band performs. And where there are pigeons, there will undoubtedly be pigeon droppings. Often venues will bring in specialist pest controllers to deal with their infestation, but this was not the case in St Louis in 2010, when Kings of Leon bassist Jared Followill found himself the target of a particular flock of feathered menaces.
After a couple of splatters landed on his clothes during the first two songs, he was hit on the face, close to his mouth, and the band elected to call a halt to their set for health and hygiene reasons.
3. Getting bored of your own music
There must come a point for any performer when it feels like they need to change gear a bit, take a break and refresh their sound. Perhaps the worst time to make that decision is just before a major US tour, as Iggy Azalea did in 2015, cancelling the entire jaunt and claiming she wanted to stop "singing the same songs".
After apologising to fans on social media, she later gave an interview with Seventeen magazine, saying: "I feel like I'm at the end of an era now. To go on a tour in late September and to stay in that mindset of what I'd envisioned for that tour, I feel like that would stifle me...
"It's not easy to decide that the best thing to do is cancel a tour, but that's the best thing for me. I don't want to disappoint my fans. I feel really bad. It was a tough decision to make, but it was the best thing."
4. Kissing Alex Jones
A cautionary tale for celebrities who push their luck. The One Show's Alex Jones recalled how a meeting with Lionel Richie ended badly for him, thanks to a bug she'd picked up shortly before his arrival. She explained to the Sun: "I'm not ill very often but I remember the norovirus was rife at the time and I started to feel very dodgy.
"I had a day off but then I probably went back into work a day too early so I was still infectious. After Lionel and I had just finished our chat on the show, I went to give him a kiss on the cheek and he went in for the lips. He caught the norovirus off me and had to cancel two of his tour dates. I did feel a bit guilty but, essentially, don't be so forward Lionel! If he'd gone for the cheek, he would have been fine."
5. Too many fans to choose between
In Ireland, 2014 was not a good year to be a Garth Brooks fan. The country star had announced a series of five concerts in Dublin's Croke Park that July, and sold some 400,000 tickets, only to discover that a license had only been granted for three of the shows, after complaints about disruption from local residents. The final two would have to be cancelled or postponed. Garth objected, saying upsetting fans on that big a scale would be like “choosing between his children”. Intensive discussions followed with Dublin City Council, questions were asked in the Irish parliament, but in the end, even an offer to postpone the final two concerts to another time, with a sixth added as a sweetener, fell through.
6. Making a sandwich
Neil Young is known for many things: his high keening voice, his poetic songs, his probing, explosive guitar solos, his general air of orneriness towards digital media. He's not known as a maker of sandwiches, and that's probably a good thing, given that it was the simple act of slicing a ham sandwich in half that caused the cancellation of a major world tour. In 1997, just before embarking on a tour of 16 countries across Europe (including a Glastonbury appearance), he picked up a knife, aimed it at his lunch, and cut the top of his finger off. Doctors examined the wound, and advised him to steer clear of guitars while it healed.
Neil later issued a statement, apologising for the cancelled gigs and saying, "I'd have eaten the thing in one piece if I'd known that cutting it in half would jeopardize the tour. It's macaroni and cheese from now on."
7. Having your leg lengthened
There are many stories of musicians cancelling gigs to go under the surgeon's knife, from Adele's vocal cords to Andrew Ridgeley's nosejob, but Rivers Cuomo of Weezer has perhaps the best. In 1995, at the height of the band's first flush of success, he pulled out of a number of gigs in order to rectify a discrepancy in length between his legs.
His left leg was 44mm shorter than his right, and while suffering what, according to LA Weekly, he later called "a huge inferiority complex about being a rock musician" he elected to have the necessary surgery to lengthen his leg, effectively stopping the band. There was an upside though, during his lengthy recovery, he enrolled at Harvard to study classical composition.
8. Snow on the roof
There's a fantastic blog post by BBC Radio Ulster presenter - and former press officer for Mötley Crüe - Stuart Bailie, in which he describes the day he had to tell the music press that the band's December UK tour had been cancelled as the venues were struggling to deal with an abundance of snow on their respective roofs.
An unlikely story? Well yes, as Stuart explains: "I'm lying, of course. I have been briefed by the offices in New York and London to put out this fabrication. The truth is that Nikki Sixx, bass player with the Crüe... had died of an overdose on December 23. Fortunately the paramedics had arrived on the scene and one of them (a fan of the band apparently) had administered two adrenaline shots to the heart. The musician had been saved, but the tour was off.
"Lucky old Nikki escaped from the hospital wearing just his leather pants and eventually got to write a bad song about the experience called Kickstart My Heart".
9. Too much potato
This story has attained such mythical proportions that it's easy to forget how dramatic certain elements of it really are. In May 2005, Brian Harvey, lead singer of East 17, managed to crash his car while falling out of it, severely injuring himself in the process, and it is all the fault of the humble potato. He explained to GMTV: "I’d been stuffing my face with jacket potatoes. They were big. I put cheese on, then tuna mayonnaise and I ate the lot."
This left him feeling unwell, and while driving to a friend's house at around 1am, he pulled over, opening the driver's door so he could throw up. "Instead of putting my foot on the brake, I hit the accelerator and it flew back," he said. "It must have hit four or five parked cars and thrown me out of the car." He then fell under the moving vehicle, which crushed his pelvis. It was six months before he could walk again.
10. Being interrupted while towelling the stage dry
Last year, Justin Bieber called off dates during his Purpose world tour, citing "unforeseen circumstances" and later telling reporters he planned to relax and "ride some bikes". His decision created a debate around what would constitute valid reasons for cancellation, with John Mayer defending the decision, and Justin's manager Scooter Braun saying, "A man's soul and well-being I truly care about came first and we must all respect and honour that".
It wasn't the first time Justin had walked. In 2015 a concert in Oslo was cut very short over a concern for his health and safety. During the first song, Justin noticed that there was spilled water on the lip of the stage, which could've caused a slip hazard. So he grabbed a towel to mop it up. Unfortunately, his frenzied fans saw an opportunity to snatch at the towel, his hands, his feet, and generally squee. This did not sit well with Justin, who requested they stop, and then, when they didn't, said, "I’m done, I’m not doing the show," and left the stage.
He later apologised to the people further back in an Instagram post (above), saying: "In no way did I mean to come across mean, but chose to end the show as the people in the front row would not listen. Hopefully people will understand where I am coming from. I don't always handle things the right way but I'm human and I'm working on getting better at responding not reacting."