This was a BTLP original, shared a whopping 8,959 times on Facebook. One photographer (and Corbyn fan) claimed that the Corbyn picture was "Photoshopped" and posted several screencaps to support his theory. He says that Corbyn's thumb was manipulated to complete the salute, but several of our followers were quick to point out that the corresponding pattern on his opposite shoulder is also blurry (due to a combination of poor light, poor focus and the fact that Corbyn is wearing some kind of shellsuit top that is crumpled all over the place, unlike his smartly dressed companion).
If the original image was Photoshopped, it went on to fool the Daily Mail, the Telegraph, Express and Metro, to name a few, but in any case there was no denial from Corbyn or Labour.
The man has a track record in such things. Photoshop is not required.