Much has been made in the British press about $FTSE running inversely to $GBPUSD because it is in reality a USD index. Certainly the path is much clearer in USD. To trade this, you have to buy $FTSE and sell $GBPUSD to create a synthetic.
In the Brexit spike, the fat finger spike, and the Trump spike, in each case we got around 61.8% retracement before a further fall. However, if you overlay Aug-Oct 16 price action to now, it gives a clear fit to Trump action, suggest a further fall (in USD).
This is one of my wilder hypotheses, btw