When you can see well ahead and the road conditions are good, you should
You MUST NOT exceed 70 mph (112 km/h), or the maximum speed limit permitted for your vehicle (see Speed limits table). If a lower speed limit is in force, either permanently or temporarily, at road works for example, you MUST NOT exceed the lower limit. On some motorways, mandatory motorway signals (which display the speed within a red ring) are used to vary the maximum speed limit to improve traffic flow. You MUST NOT exceed this speed limit.
The monotony of driving on a motorway can make you feel sleepy. To minimise the risk, follow the advice in Rule 91
You MUST NOT reverse, cross the central reservation, or drive against the traffic flow. If you have missed your exit, or have taken the wrong route, carry on to the next exit.