That is a double mattress on its side that it is draped over, so you can tell that it is quite wide. And it was when I draped it there that I realised I had perhaps overestimated the number of blocks required.
I have always liked zig zag quilts but loath patchwork with triangles so loved this idea of working on the diagonal when I came across it on Pinterest. I was trying to think when I cut out the pieces, since this is a project I brought with me from the UK, at which time only about half the colour/white squares were sewn and trimmed to size. It turns out it was a year ago exactly give or take a couple of weeks. I linked to the tutorial in that post.