Complex sentence: In parliament he was promoted to the frontbench as a spokesman on home affairs by David Cameron on becoming Leader of the Opposition in 2005, and he has also been a member of the home affairs select committee since 2005.
Split into simpler sentences: In parliament he was promoted to the frontbench as a spokesman on home affairs by David Cameron when Cameron became Leader of the Opposition in 2005. Herbert has also been a member of the home affairs select committee since 2005.