Complex sentence: The original station facades on Kingsway and High Holborn were uniquely of granite but were destroyed by 1930s replacements but, uniquely, the adjacent facades at ground and first floor of the building in which the station is situated were built to the same design using Portland stone.
Split into simpler sentences: The original station façades on Kingsway and High Holborn were uniquely of granite but were destroyed by 1930s replacements. The adjacent façades at ground and first floor of the building in which the station is situated were built to the same design using Portland stone.