Dear Women of London,
It is May. Mid-May. PUT AWAY YOUR BOOTS. Yes, I know today is the first day in many that the weather has been less-than-ideal. But that does not mean you get to whip out your boots like that spat of 70-80 degree days never happened. There are other options. It's not as though it's either sandals or boots. This time of year is exactly why ballet flats exist. Get thee to a shoe store and discover the plethora of options that await you.
P.S. There is but one exception to this rule: Hunter wellies.