We introduce a property for a couple of topologies that allows us to give s
imple proofs of some classic results about Borel sets in Banach spaces by E
dgar, Schachermayer and Talagrand as well as some new results. We character
ize the existence of Kadec type renormings in the spirit of the new results
for LUR spaces by Molto, Orihuela and Troyanski.