The pound has formed and remained within a long-term trading range since October 2016, in which month the low of the range was set. The high of range was set in the week that commenced January 29, 2018, with the range of prices spanning from approximately 126.670 to 155.500. Using the weekly candlestick chart, I illustrate this with the shaded area.
(Chart created by the author using TradingView. The same applies to all subsequent candlestick charts presented herein.)
The red line in the chart above depicts the midpoint of the trading range, which has evidently