Earlier quoted context omitted.
Dog attacks are common enough in the U.K. to be a topic you can subscribe to on the BBC news site. While it’s definitely pretty culturally acceptable to have a dog off leash there, I’m not so sure it should be, especially in places such as children’s parks or near livestock etc. https://www.bbc.co.uk/news/topics/c9q9301541xt/dog-attacks
Strangely enough, most of those stories are about dogs attacking their own owners/families and seems to indicate the dogs were leashed in most stories.
The dog was on the lead (or leash for you American English speakers) at the time of the attack though.