There are many reasons to switch to HTTPS - protecting financial data in transit is just one of them. Here's an overview with further explanations but many similar examples exist: https://snyk.io/blog/10-reasons-to-use-https/
When I see bank + policy + not just some random bank but the BANK OF ENGLAND, I do expect to see HTTPS guaranteeing the integrity of what is unquestionably important and influential data being served to decision makers.
This amused me, but maybe I'm just easily amused.