Adele is a Grammy Award-winning artist whose powerful, soulful sound has made her an international success.
Adele reportedly wants to ensure her new album is perfect in every way before it's released.
The 26-year-old singer hasn't released an album since her Grammy-winning ‘21’ in 2011.
"I flew to London to work on new stuff with Adele last year,” Diane told newspaper The Sun.
"We did some great songs but I don't know if they've made the record. I don't think anybody does.
"She has a mind of her own. Nobody rushes Adele or makes decisions for her, which is probably why she's a great artist. She wants to get it right."
Adele is said to have been working with a number of well-known musicians on the highly secretive album.
It has previously been reported that Adele has been working with OneRepublic frontman Ryan Tedder.
"She is delighted to have such a talented writer and performer working with her and for Ryan it is a massive privilege," a source told the newspaper.
Watch Adele 's music video for her hit 'Rolling In The Deep':