I've come at this one from a few angles over the years. Right now I work for a firm that produces software to manage data-privacy issues and compliance so, although I'm not on the lawyering side, I do work with people who are experts in the field. I also do a bit of amateur photography - mainly sporting events - and have come across the occasional jobsworth or "I know my rights" type over the years.
First off there are very few restrictions about taking images in a public space. The key here is what counts as "public". Certainly (again with a couple of exceptions around terrorism, sites covered by the official secrets act and, bizarrely, commercial photography in Trafalgar Sq ) the public highway is exactly that. Same with any facility that's not specifically owned by a private body, so public parks are also good. Many people are surprised that there's no law that stops you bringing a camera to your local park and taking pictures of the kids playing there. Whether that's a good idea is another argument and I certainly wouldn't, but people are quite happy for parents to livestream the same scenes from their mobiles on to any number of social media platforms with fair use policies that are anything but.
However, privacy law and how it relates to images of people does have some subtleties. Without any other identifying information, a movie of your journey to work won't have any privacy implications, even if you film any resulting "discussion" with a fellow road-user about misconceptions around the UK's current road-funding model. But, if you then passed on that footage to the police and they attempted to identify that road-user by cross-referencing with other data points, then that footage would fall under the
police's GDPR responsibilities.
I've a few real-world examples from my own experience, including a long-running saga with the National Ice-Skating Association, but I'll spare you those.
As always, I point people towards the
ICO website. I've had some people tell me it's "useless" when what they really mean is that it's giving them an answer they don't like, but it's generally well written and the many examples can be illuminating.