[NikkiA]

¬ is one of the many 'not' symbols that has been used through history.

As to why UK keyboards include it? Probably IBM, ¬ was the negation/not symbol in Z, it wouldn't surprise me if Hursley Park petitioned the rest of the company to ensure it was on the UK PC layout.

(This Z: https://en.wikipedia.org/wiki/Z_notation )

[rhinoceraptor]

It makes a good EOL character to highlight trailing whitespace.

[NikkiA]

True, but unicode gives us ⏎ which is pretty unambiguous