Speed/obstruction question

[Adrian W]

my journey to work follows about 20 miles of country A road, it is not the sort of road you would make a habit of overtaking on, recently a woman in a Hyundai has started using this road but she does the whole 20 miles at 25MPH, the queue behind her becomes huge, this has been going on for a couple of weeks now, you can imagine the drivers frustrations behind her, is she actually doing anything wrong?

[Adrian W]

Thanks chaps, I wasn't sure if the attitude would be 60 is the maximum allowed speed etc etc, today I was the first car behind her, normally I'm quiet a way back.