Sadly, Ed’s grandmother passed away while he was recording Divide and in an interview with MTV, he revealed his reaction to her death was to write a song. 

“...that's my first reaction for anything that happens to me, good or bad, pick up a guitar," he said. His grandmother was in the hospital near the studio where he was working, so he visited with her frequently.

It was originally written in memoriam of his grandmother, strictly as a tribute to her life. Out of respect, he didn’t feel it was right to put it on Divide. As he explains in a conversation with Zane Lowe, after playing the song at his grandmother’s funeral, his grandfather turned around and told Ed to put the song on the album.

The lyrics are true, Ed explains. He wrote about the small things, the things she left behind. When he wrote that she was an angel in the shape of his mother, he meant it. “She was, like, the nicest woman you’d ever meet.”

“Supermarket Flowers” is written from Ed’s mother’s point of view. This is probably why people thought it was Ed’s mother in the song, not his grandmother — but the angel in the song is, as confirmed by Ed, “my mum’s mum.”