Taylor Swift offered to delay the planned launch of Evermore by a week to avoid hijacking Sir Paul McCartney's original album release date.

The pop superstar stunned fans last week by dropping the follow-up to July's secret album, Folklore, just hours before it hit streaming services. McCartney has now revealed he knew all about the surprise project - because Swift had given him a heads-up as he prepared to unveil his latest material, McCartney III, which ended up being delayed by a week due to production issues.

The legendary musician, who recently chatted with Swift for the cover of Rolling Stone magazine, shared the news in a Tuesday morning interview with radio personality Howard Stern, after discussing how the Beatles used to coordinate releases with rock rivals the Rolling Stones to avoid chart clashes during their heyday.

"I did the Rolling Stone cover with Taylor Swift and she just emailed me recently and she said, 'I wasn't telling anyone, but I've got another album... I was going to put it out on my birthday' - which I think was the 10th," McCartney recalled.

"And then she said, 'But I found out that you were going to put it (McCartney III) out on the 10th so I moved to the 18th.' And then she found out we were coming out on the 18th, so she moved back to the 10th. So, you know, people do keep out of each other's way," he explained.

"It's a nice thing to do," McCartney added.

Evermore officially debuted on Friday, two days before Swift turned 31.