Almondsbury is said to have derived its name from being the burying-place of Alemond, a Saxon Prince, and father of King Egbert; but more probably from a burg, or fortification, constructed by him, and the remains of which are yet visible on an eminence to the eastward of the Church. The traces of a Camp are also discoverable round the brow of Knowle Hill, within the area of which is the Manor-House [..].
From ‘The Beauties of England and Wales’ v5 (1810).
Witt’s 1880s Handbook calls it ‘Knole Park Camp’ :
This stands on a steep hill in the parish of Almondsbuary, six miles north of Bristol. Though conforming to the shape of the ground, the camp was nearly oval. The defences consisted of a mound and two ditches, but these have been mostly destroyed by buildings, a large house having sprung up within the area of the ancient camp. There seems to have been an entrance at the north-east end, but nothing very definite can now be said on the subject. The views from this position are very fine, and embrace both shores of the Severn and the district of the Silures.
The fort doesn’t seem to be a scheduled monument? Maybe it’s just been ruined too far.