Dido tbh, even though she's one of my favourite artists.
I feel like other singer-songwriter gurls have taken her place, and the 5-year long gaps between albums certainly don't help her either.
Her album sales over the years:
22 million - 12 million - 1 million - 400k
I feel like she'll still have a top 10 album in the UK whatever she releases, but her days of ruling the charts are gone.
Also Mika.