After a week long geek festival, my boots were looking rather tired. The front sole was breaking away and flapping loose. I had some black Sugru left over from another fix so thought it was worth a try.
I just bunged a good bunch of Sugru at the front and kneaded it together until it looked about right. Left to dry. Appears to be a good fix.
Sugru courtesy of their build night event at my local hackspace.