Complex sentence: Since Hong Kong was created a British colony in 1842, those who were born in the territory or become naturalised had British nationality, which included the right to enter and live in United Kingdom in addition to Hong Kong.
Split into simpler sentences: Since Hong Kong was created a British colony in 1842, those who were born in the territory or become naturalised had British nationality. This included the right to enter and live in United Kingdom in addition to Hong Kong.