Featured image not showing

Hi,
I have an image which when used as a ‘featured image’ previews OK, but does not display when you log out and view the page on its own, I have googled this and made sure the image is wider than 620 pixels.

Here’s the page:
http://www.upwards-and-onwards.org.uk/the-low-rider-is-a-little-higher/

Any ideas.