Complex sentence: Len Cook was the first Director to hold the newly created role of National Statistician and the roles of Director of ONS and National Statistician were combined until 2012 when Jil Matheson continued as National Statistician while Glen Watson became Director of the ONS.
Split into simpler sentences: Len Cook was the first Director to hold the newly created role of National Statistician. The roles of Director of ONS and National Statistician were combined until 2012 when Jil Matheson continued as National Statistician while Glen Watson became Director of the ONS.