Although if you look at the actual text on the UKUSA agreement document HW 80/2 [1], rather than the short synopsis from Wikipedia, it says very clearly that th

Although if you look at the actual text on the UKUSA agreement document HW 80/2 [1], rather than the short synopsis from Wikipedia, it says very clearly that the UKUSA agreement covers only sharing of "foreign communications" where footnote 3 on page explicitly excludes communications of both the UK and the USA. 1. https://discovery.nationalarchives.gov.uk/details/r/C11536912 https://discovery.nationalarchives.gov.uk/details/r/C1153691...