MI5 is Britain's domestic intelligence and security agency, analogous to the FBI. If this story is disinformation, then MI6 was most likely responsible.
A lack of access to British bases will inconvenience the US military in this instance, but won't stop or even meaningfully delay US strikes against Iran.
So from an operational point of view, what would be the value of such disinformation?
Haven't thought much about this, but my instinctive suspicion is that the British are looking for American concessions elsewhere in exchange for access to forward basing for hitting Iran.
Most likely a harder line on Russia.
Trump is more subdued than usual, but
is most likely what you had in mind from him:
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