I propose for the UK government to make it a legal requirement to ensure all businesses and service providers accept cash as payment.

The emergence of online banking & payment systems have been happening at such a fast pace that there has not been enough time to put proper safeguarding measures in place to tackle and properly mitigate the effect of any large scale cyber attacks that we have been recently warned about in the media / The World Economic Forum (WEF). 

In the event of such we need to ensure trade will suffer minimal disruption only, hence cash must remain as an accepted method of payment by all retail businesses, service providers etc.