Complex sentence: This was built only as a temporary measure to last the duration of the war however after the end of the war in 1946 the buildings were left standing and in 1948 the hospital was handed over to the newly formed NHS to become Sedgefield General Hospital.
Split into simpler sentences: This was built only as a temporary measure to last the duration of the war. However, after the end of the war in 1946 the buildings were left standing and in 1948 the hospital was handed over to the newly formed National Health Service to become Sedgefield General Hospital.