The evaluation was undertaken in two phases: first, in 2018 through to early 2019; and second, in late 2019 to mid-2020.
Cynhaliwyd y gwaith gwerthuso mewn dau gam: yn gyntaf, 2018 hyd at ddechrau 2019; ac yn ail, ar ddiwedd 2019 hyd at ganol 2020.