I want to start a food business, anyone know what sort of authorisations are needed?

i'm thinkin to purchase a caravan and start a "remote sandwich shop", i havent got experience in the food sector,but i'm able to get hold of the capital needed though and can find someone to work for me, anyone been in this sort of business and can give me some advice in terms of where the place to start would be and what legal requirements there are? thanks for your help