That tyre buried in 1970 .... it was a Good Year !
It was the Michelin Man wot dun it :-)One of these at http://images.google.co.uk/images?q=michelin+man&hl=en&rls=GGLR,GGLR:2005-50,GGLR:en&um=1&sa=X&oi=images&ct=title has got to be the logo for Atkinson's 'work' at Silbury.
Choose yer favourite - I'm going with 4th line, 2nd across ;-)