With the announcement of the UK / European Union deal late on Friday night, we have a good reason to look at the currencies compared to the US Dollar ($USD).
A macro view of the British pound ($XBP) shown in the centre panel suggests a rising pound is generally bullish for both the $FTSE and the $SPX. Currently, the $XBP has bounced off support with a low of 141. The majority of the time shown, the pound has traded above 140 and below 170. We are at the low end of the range.