Justification for works to a Listed Building

When is this required: 

For all internal and external alterations to a Listed Building. 

What information is required: 

A statement setting out why the proposed works are required to be undertaken.  This may be repair works due to maintenance concerns, or may be a proposal to the change the internal layout due to a change of use of the building.  The statement should give clear advice on why such works are necessary, any delay in this information may result in your application not being validated.