Sub division sale revenue versus secured loan reduction

[Littleguy]

We have an old farmhouse and a parcel of land which has a secured loan against it. Our bank agreed to the sale of part, (approx 20%) but then demanded all proceeds of sale, approx 65% of total borrowing, whilst telling us that we would be able to retain approx half of revenue to allow further development. Is there any kind of rule or convention regarding this kind of thing? (Ignoring the question of the bank misleading us and our solicitor going along with it!) Seems wrong to us as we cannot continue our development without the promised revenue. We now have LTV of approx 30%. Can banks just do this?