The four criteria for assessing class importance apply to banjo enclosures as follows:
- Period (currency): Restricted. Present evidence suggests that the tradition of constructing and using banjo enclosures was mainly a feature of the middle Iron Age with some sites continuing in use during late Iron Age times up to a maximum of perhaps three centuries.
- Rarity: Rare. It has been estimated that about 200 examples have been recorded to date, mostly in Wessex and the upper Thames area. Outside these core regions banjo enclosures seem to be very rare.
- Diversity (form): Medium. Four main types of banjo enclsoure can be identified on the basis of ground-plan and the combination of main components.
- Period (representativity): Medium. Banjo enclosures are one of a fairly wide range of Iron Age monuments, including many other classes that are known to have been settlements.
Assigning scores to these criteria following the system set out in the Monument Evaluation Manual, banjo enclosures yield a Class Importance Value of 21. This lies about one-third of the way up the range of possible values (max.= 64), emphasizing the geographically localized and chronologically restricted nature of this particular class of monument. Examples representing the full range of types, and variations in size and orientation, must be included in the sample of nationally important sites, and special attention should be given to the inclusion of examples in areas where banjo enclosures are rare.