I think we need another "Bojo at the table looking serious" address to the nation making it clear that if you're not moving you're not exercising, except a short rest standing up. Most people I think are just ignoring the Press Conferences now.
That said, such a ban may well have unintended consequences, such as people going shopping more often so they can walk to the supermarket and get exercise that way.
I think the Police and others also need to use some common sense, for instance stopping people exercising on their own in beauty spots is a bit silly, but it would be totally valid to go and give tickets to people sunbathing in groups because the latter is a clear infringement.
I also wonder if it would, though some families may not like it, be sensible to impose legal restrictions thus:-
- No children (I'd go with under 16 for this) may be in public without being accompanied by an adult (over 18), and that a £30 FPN will be imposed on the legal guardians of such children if the Police have to catch them and take them home
- No groups in public, even of family units, may include more than one adult (over 18), unless one of them is a carer for someone with a disability
Those would make enforcement easier because it would be easy for the Police to see, and take a single photograph in most cases easily proving, that an offence had been committed. Without compulsory identity it's impossible to check people don't live together, which is rather a challenge.