I posted this question in July under History & Myths. I got some good answers but no definitive answer. It was about a site I found called "Derelict London". One of the photo's is of a sculpture embedded in an arch of a sort of imp. It is in the "Parkland Walk" a disused railway line. It ran from Finsbury Park via Stroud Green and Crouch End to Highgate. The "imp" sculpture is sited as you approach Crouch End Station. The photo taker doesn't know anything about the sculpture, but I'm intrigued. What is it, who made it, etc?
According to one website, it is a spriggan , which relates to Cornish folklore. It is said that these cousins of the pixie, which grow into giant form, will put acurse on anyone who mistreats the pixies.