In the summer, perhaps just when you're going to the beach, it's common to drive in flip-flops to avoid the inconvenient hassle of carrying two pairs of shoes. However, regardless of what the law says , you should always be aware of potential safety risks: for example, the flip-flop straps could break or get caught between the pedals.
From this perspective, closed shoes don't have these problems, being objectively much more comfortable for proper driving. But let's now consider what the Highway Code requires in this regard. Until 1993, driving in flip-flops and sandals was strictly prohibited, but today the regulations have changed.
There is no longer any law prohibiting the wearing of specific footwear while driving , so much so that you could technically drive barefoot without any shoes at all. This issue is probably not so indifferent to insurance companies, who, in the event of an accident, could appeal to this detail.
Even the police report might mention the driver wearing flip-flops. What is certain is that the current regulation requires the driver to take all necessary steps to ensure the vehicle brakes promptly within its visible radius and in anticipation of any potential obstacles .
In short, it all seems to come down to common sense. And, probably, to ensure maximum safety while driving, it's advisable to wear appropriate footwear. Flip-flops, which don't allow full freedom of movement , could be dangerous when driving.