In reply to L'Eeyore:
Select photo and choose share (may be shown as an arrow). Should pop up a dialog.
(Note this gives different options depending on where in flickr you do this... From camera roll doesnt give you all the options)
Anyway select embed(or bbcode), it'll give you a very long url like this -
<a data-flickr-embed="true" href="
https://www.flickr.com/photos/96168376@N02/24400603649/in/album-72157664033..." title="IMG_3030"><img src="
https://farm2.staticflickr.com/1535/24400603649_88a6edcb22_z.jpg" width="640" height="480" alt="IMG_3030"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>
The only bit you really need is the direct link to the jpg in this case
https://farm2.staticflickr.com/1535/24400603649_88a6edcb22_z.jpg
Sounds convoluted but works fine in practice.