Simplify the following text for a Grade 12 native English-speaking person.
Original: He was first elected in 1986 in a by-election as the Member of Parliament for the West Derbyshire constituency in the United Kingdom , and since 2010 for its successor , the Derbyshire Dales constituency .
Simplified: He has been a Member of Parliament ( MP ) since 1986 , initially for West Derbyshire and since 2010 for its successor , the Derbyshire Dales constituency .