Complex sentence: In the late 19th century Alverstoke became completely built up and the fields separating it from Gosport disappeared and both formed part of an Urban District which prevented the need for creation of a civil parish.
Split into simpler sentences: In the late 19th century Alverstoke became completely built up, and the fields separating it from Gosport disappeared. Both parishes then formed part of an Urban District, which prevented the need for creation of a civil parish.