And the bit everyone forgets...
...When it is safe to do so.
If you are doing 70 in bad weather you are driving dangerously.
Rule 125 states:
"The speed limit is the absolute maximum and does not mean it is safe to drive at that speed irrespective of conditions. Driving at speeds too fast for the road and traffic conditions is dangerous. You should always reduce your speed when
the road layout or condition presents hazards, such as bends
sharing the road with pedestrians, cyclists and horse riders, particularly children, and motorcyclists
weather conditions make it safer to do so
driving at night as it is more difficult to see other road users