Also see
https://www.toyota-europe.com/world-of-toyota/feel/environment/worldwide-harmonized-light
The revised test has given the Prius higher emissions figures, although these won't affect the London congestion charge exemption zone, as TfL won't be re-evaluating existing models -
https://www.autocar.co.uk/car-news/new-cars/new-toyota-prius-co2-figures-push-it-over-congestion-charge-exemption-zone
The new test does mean that manufacturers may withdraw or modify models which don't meet the new standards - eg.
http://www.autoexpress.co.uk/volkswagen/golf/103993/volkswagen-golf-r-power-dropped-down-to-296bhp-due-to-wltp-emissions-rules