removing an overage condition from our land registry

When I bought my property twelve years ago the vendor placed a condition on the Land Registry that if I developed the land within ten years we would ahve to pay an overage charge. The ten years have passed and the condition has expired with no development taking place but the condition is still on our land registry. How do I get it removed? 

Roger - that all depends on how the 'condition' has been protected on the register itself. Can you add how it has been protected please?