Sorry, maybe I was a bit dismisive of the 50ft rule but people often post on here about it and only refer to the distance without mentioning the rest of the rule. That can mislead and could mean people missing out on being able to shoot in their garden.

There's enough restriction in this country without our adding imaginary constraints to it.

The important bit of the rule is:

The offence is complete if a member of the public is injured, endangered or even just alarmed by the incident

If you can avoid causing injury, endagerment or alarm to people on the highway you're less than 50 ft from then you should shoot.