Be very wary.
Planners, if made aware could ask that all unauthorised work be removed, and the original features restored.
If you are the current owner of the property it will be at YOUR COST.
The indemnity i assume will be an insurance policy, or similar.
Should you be required to rectify the work, enforcing this will be a civil matter and the legal costs etc to obtain this.
The planners will be less sympathetic, and you will probably need to fund the works yourself and then recover through the indemnity mechanism later.
Secondly, if the planners are aware, selling your house later without restoration will be impossible