What this question doesn't say is that both of these aircraft have been in service with the RAF for some time: according to Wikipedia, the Typhoon since 2003 and the Lightning since 2010 when the Harrier II (GR9) was retired.
Wikipedia adds that "the 160th, and last, Typhoon (ZK437) was delivered to the RAF on 27 September 2019", but "the F–35 [Lightning] is to be Britain's primary strike aircraft for the next three decades."
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