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.

Coincidentally a friend of mine was just attacked and bit by a large Alsatian. Luckily he is mostly okay!

The dog was on the lead (or leash for you American English speakers) at the time of the attack though.