The review was conducted between June 2020 and February 2021, with the majority of the work completed during July to September 2020, and January to February 2021.
Cynhaliwyd yr adolygiad rhwng mis Mehefin 2020 a mis Chwefror 2021, a chwblhawyd y mwyafrif o'r gwaith rhwng mis Gorffennaf a mis Medi 2020, a rhwng mis Ionawr a mis Chwefror 2021.