When did 'Kent variant' Covid-19 become more prevalent in Scotland?

The chart shows weekly number of samples tested by polymerase chain reaction (PCR) in the UK Government and Regional Hub laboratories in Scotland, in which the S gene was negative (referred to as S gene dropout) but one or both of the other two genes (ORF1a and N) were positive with a CT (cycle time) values of 30 or less. This is considered a good proxy for the variant of concern VOC202012/01 (Kent variant). It compares this with the total number tested for the variant each week. The variant VOC202012/01 was detected in Scotland from November 2020.