It's a very stripped back song, just voice and piano I think and the piano part is really really easy.
Anyway, my sister-in-law is 15 and is crazy about the song and loves fiddling about on her keyboard so I spent an hour last night teaching it to her. It went well and she loved it. She doesn't yet know how to read music unless the notes are written on the piano keys so I also spent some time getting her to learn the note names without using any stickers. She did OK.
I've never given any piano lessons (unlike my sister who is a piano teacher) but I found it an enjoyable hour.
Here is the tune on youtube performed live at the O2 arena
Cullum? Nah I'm more into Ben Folds when it comes to piano pop. He plays a Baldwin but I won't hold that against him