I am a little concerned as I have insured a friend to drive for me whilst I have an ankle injury. We was heading down a dual carriageway where roadworks were happening, lots of cones throughout this 2 or 3 mile stretch which is usually 60 in to a 70mph zone. To be fair he stuck to 40mph for the majority of the road, however there were only three signs stating maximum speed as 40, these were yellow signs with just text and not the usual type, also not the easiest to see as it was raining and there were tons of differing signs. These only covered the first 1/4 of the dual road which had now been coned off in to a single, once we got most of the way down the road he started to put his foot down as there was a 'no stopping, end' sign which he SOMEHOW mistook for an end of roadworks sign. I asked him why he was returning to the usual speed limit of the road, then he realised and slowed down. Now the reason I am worried is because I did see someone with an item in their hands, although likely one of the workers with a tool but I am super paranoid. We drove it back around to have another look, couldn't confirm this. We did notice though even after the road returned to a dual carriageway that there was nothing to say the speed limit had returned to normal.

This was quite late at night, around 11pm? I know there were no fixed cameras, I am just extremely worried about the speed guns. If what I saw was in fact a speed gun, would we have been stopped immediately? Does he have any reasonable explanation, should signs have been implemented for most of the road? Also if it was a speed gun and he happened be going 20+ over the limit, how long would contact take? Sorry about my English, its my second language. Thanks!

I would not worry about it. Not likely to be a handheld speed gun at that time of night. And any speedgun would need to be used by a Police Officer or other authorised person.

I doubt you will hear anything.

Speedgun or not (which I very much doubt) there would be nothing done.

Speed signs of black lettering on a yellow background are advisory only, they are not mandatory and cannot be enforced by law. So as long as the diver did not go above the statutory speed limit for the stretch of road in question, a speeding office did not take place.