I don’t think you can be prosecuted in a 20mph zone for speeding, you can if it’s 20mph limit. You’d need to research a bit more;
https://www.20splenty.org/police_enforcement
[URL]https://www.rospa.com/rospaweb/docs/advice-services/road-safety/drivers/20-mph-zone-factsheet.pdf[/URL]
https://www.20splenty.org/police_enforcement
[URL]https://www.rospa.com/rospaweb/docs/advice-services/road-safety/drivers/20-mph-zone-factsheet.pdf[/URL]