It's not just the Daily Mirror, it's the Daily Mirror comic strip - which means, it's Jane (ie the original comic strip in both senses of the word). That's quite a subtle reference (it took me several days to cotton on) but it's worth noting that Jane was a cult, making it quite OK to buy the paper in certain environments (eg wardrooms?) just for the comic strip, in the sort of annoying self-referential slumming that makes Oxbridge JCRs buy the Sun, or at least they did in my day, but it's also got a theme of spies and spying (usually so that Jane has to take off her clothes to change into disguise) including the glamorous antagonist, Lola Pagola, the beautiful spy (the Guardian - incidentally, iirc, the Manchester Guardian is bought for Edwin's benefit in TRMF and I recall thinking "And you can see the problem right there" when I spotted that detail - ran a sort of updated parody in the 70s called Varoomska, in which the Jane figure was Russian)