This forex pair represents the British Pound - Canadian Dollar cross. This Sterling ('base currency') is one of the heaviest traded pairs in the world. The Loonie ('counter currency') is typically considered a commodity currency due to Canada's reliance on energy exports for growth.
Congestion is the status quo whether the focus is equities, FX or some other asset class. Yet, there are always the outliers, and GBPCAD happens to be a very prominent example with a near 8 percent tumble.