parkrun — free weekly community 5k and junior events

parkrun organises free, timed 5km runs every Saturday (and free junior 2km events on some days) in public parks and open spaces across the UK; events are volunteer‑led and free to enter after a one‑time online registration. Anyone can take part regardless of pace or experience — you register on the parkrun website to get a personal barcode, turn up at any registered event and have your time recorded for free. It’s an established community fitness programme with thousands of regular participants.