Hello I am a solicitor with over 15 years experience. I will try to help you with this.
If you are talking about average speed limits then we are talking about the average speed of one vehicle through a measured distance.
Temporary average speed limits certainly can be legal. The are typically used at eg motorway roadworks.
So the NIP states you have been caught driving at 61 MPH in a temporary 50 limit. Is this your average or have you been cuught by a specific camera doing this specific speed. Do you have any point son your licence?
As far as temporary speed limits are concerned an application must be made to the local authority who will grant approval for a specific time and place. There must also be adequate signage to notify of the change.
In terms of sentence for doing 61 in a 50 mph zone you are looking at a small fine and 3 points.
Thank you for your secondaary replies which I found interesting.
I have no points on my licence and have never been found speeding before by any fixed or mobile speed cameras - been driving for 40+years.
I need to check on the average, or specific, question you raise as I am unsure.
Is this something that I should 'roll over' on, or would it be economical to contest..an winnable ?!
Not yet - just received the notice to prosecute.