Who carved the Paulsgrove Skull?

Paulsgrove Skull Sign
Paulsgrove Skull Sign

There’s a skull in Portsdown Hill. I don’t know how long it’s been there, but carved on the wall of an old cave there is a spooky face. It is mentioned and pictured by the great local resource Portsdown Tunnels. There is also a sign outside which shows a painting of the skull along with a falling rocks sign.

Does anyone know anything about this strange thing?

*** Update 24-1-2013
I just got this tweet with a bit more info:

@PortsdownHill#paulsgrove_skull update – apparently carved by pupils from King Richards school after the Paulsgrove estate was built (1940s)

I’d love it if anyone involved could contact me either here or via twitter (@straywasp)