deferred tax–Mike little et al please help!!

Believe it or not,doing P2 and i’m still in a tizzy with deferred tax..Please can someone explain it..didnt really have a good foundation in it..never have understood the core concept..
If the tax base is zero for example(100% capital allowance)..it means no tax is chargeable on the asset..at least for that year..How then can the asset still have future/deferred tax charges?
Or is it like an assumption that the asset may be sold and so will be liable for tax if sold and therefore provide for this? (prudency concept)
Please someone help…!!