Snowfall in London

Hi guys,

I'm having a surprising amount of trouble finding a very simple piece of information: how much snowfall does London, England usually get? I've Googled lots:

History weather UK
Snowfall in UK
UK climate
Precipitation in UK
Amount of precipitation in UK

A note: My story is set in 1975, so this would be before the major climate change of recent times.

<B>As usual, incredible response. Thank you to everyone!</B>