By reason of form and poor design of the proposed side extension, it is considered that the proposal would result in substantial harm to the character and appearance of the host dwelling and the surrounding area. The proposal is considered to be contrary to Strategic Policy C and Policy CO17 of the Authority's Adopted Policies within the NYM Local Plan, together with the Authority's adopted Design Guide Part 2: Extensions and Alterations to Dwellings. These policies and guidance seek to ensure that new development achieves a high standard of design, which reflects or complements that of the local architectural vernacular and does not detract from the character, form and setting of the original dwelling or the wider area.