These earthworks (probably an Iron Age hillfort reused in medieval times) – are where the giant threw the Tibblestone from.
I haven’t found an older reference for this, but Danny Sullivan claims the giant was aiming at Tewkesbury:
hoap.co.uk/aatf1.rtf.
whilst Celia Haddon says he was aiming at the boats on the Severn:
celiahaddon.co.uk/standing%20stones/gloucestershire.html
That’s really the wrong direction! but then, it is said that he slipped mid-throw.
The ‘Tibblestone’ page quotes ‘The Old Straight Track’: “A long time ago, a giant lived in these parts, and he went up the hill to fetch a large stone to destroy his enemy’s house. When he was carrying it down, his foot slipped, and his heel made a great furrow in the hillside, and you can see it to this day, and he had to drop the stone just where you see it. It is quite true because you can see for yourself the holes where the giant’s fingers had hold of it.”
tibblestone.users.btopenworld.com/tibblestone.htm