Cannot update Photoshop

I tried to install the updates on Creative Cloud that came through this morning, for Illustrator and Photoshop; the first worked fine but the Photoshop update failed at about 54% with a message to close all running instances of Photoshop.

I had just booted my computer and hadn't run any programs at that point - Photoshop was certainly not running.

I downloaded the patch file to update manually but got the same error message with that.