The King hitmakers have been serving as the British pop star's opening act on the North American leg of her Delirium World Tour since the beginning of April (16), but earlier this month (May16), Olly fell ill and the band had to unexpectedly cancel a string of appearances.

At the time, he took to Twitter to apologise for the sudden no-shows, writing, "Hello bbs (babies). ThankU for all ur nice words and support and good health wishes - I got some weird viral illness about four days ago and I've not really been able to get out of bed since."

And it appears his condition isn't getting any better, and the band has cancelled its remaining U.S. tour dates with Ellie.

A statement on the Years & Years Twitter page reads: "It is with great regret and sadness that we have to cancel our remaining US shows with Ellie Goulding, it has been no secret that Olly has been unwell recently and we have been advised that he needs immediate rest to make a swift and full recovery. We are very sorry and want to say a big thank you to Ellie and her team for having us and to everyone that came to see us."

Luckily, the band will only be missing five tour dates, as Ellie wraps up the North American leg in Houston, Texas on Saturday (21May16).

Years & Years are also expected to join Ellie for her dates in Australia and New Zealand in September (16).

Meanwhile, Ellie made the most of her support group's last-minute cancellation by serving as her own opening act on Monday (16May16) at a gig in St. Louis, Missouri's Chaifetz Arena.

The Lights star surprised fans as she walked onto the bare stage with an acoustic guitar, telling the crowd there was "kind of a situation where I didn’t have any support acts, so I’m just going to play. I didn’t want you to go without anything."

Ellie went on to perform an impromptu acoustic set for 20 minutes, and ended with a cover of Elton John's Your Song. After taking a 30-minute break, she was back on stage with her band.