England and Wales have a genuine 'right to roam' over large areas of mapped Open Access land — mostly moorland, downland, heath and some coast — and the Countryside Code sets out exactly what's expected of dog owners using it. The core instruction is to keep dogs under effective control so they don't disturb wildlife, livestock, horses or other people, with a short lead specifically recommended around sheep and ground-nesting birds.
One rule is a fixed date rather than a judgement call: on Open Access land, dogs must be on a lead between 1 March and 31 July every year, regardless of whether livestock is actually present on that particular stretch at that particular time. This covers the main lambing and ground-nesting bird season, and it applies across the whole period, not just where signage happens to be posted.
The Code is also direct about consequences: if a dog is genuinely threatened by livestock or horses, the advice is to let it off the lead rather than risk personal injury trying to control it. And the reverse situation carries real legal weight too — a farmer can lawfully shoot a dog that's attacking or chasing livestock, and may not be liable to compensate the dog's owner for doing so.