Complex sentence: Nottingham City Council wholly own the company making it the first local authority energy company since the UK energy market was nationalised in 1948 under the Electricity Act 1947 and subsequently privatised in 1990 under the Electricity Act 1989.
Split into simpler sentences: Nottingham City Council wholly own the company making it the first local authority energy company in the UK. Prior none had existed since the UK energy system was nationalised in 1948 under the Electricity Act 1947 and subsequently privatised in 1990 under the Electricity Act 1989.