2 metre distance...

The point of the mask, as far as my research tells me, anyway, is that if you have covid symptoms and wear a mask, if you cough or sneeze (or breathe heavily) the droplets don't spread as far. The idea is that everyone should behave as if they are infectious. The mask protects others, not yourself..

There was a German video doing the rounds on twitter yesterday with illustrations of distancing if you are behind someone and you are both moving. Stay back 4 metres for walking, 10 metres for running and 20 metres for cycling.

I suspect that it's a good idea to try to never stay behind anyone who is moving for long if you can possibly avoid it

Video here:
twitter.com/globaljukeboxer/status/1259391695772319744

I think you should do what you feel comfortable with. If in the workplace you cannot run a business 2 metres apart for long, but pensioners can do what they please.

I wear one every time I go shopping (once a week)..on my walks I rarely pass anyone because of where we live...

So do what you can to minimise risk, ok a mask won't 100% protect you, but better than nothing?

A cough and a sneeze can travel 25/26 feet.