This can be achieved over time in career mode or can be completed much more quickly by going into quickplay.
>select the Wales Rally GB
>select stage Great Orme reverse
>make sure you toggle the time of day to "Night" (all other settings can remain default)
>select your car and drivers
>this is one of the shorter stages; I personally can complete this stage in less than 3 minutes consistently. So using this method would take roughly 25-35 minutes depending on your skill set.
Now the focus is winning the 10 stages. For those who are not as experienced in racing games, don't take unnecessary risks. It's all about cornering, apex, apex, apex! Focus on approaching corners, make sure you aren't going too fast and accelerate as you're exiting the corner. Don't get discouraged if you make a mistake, time can easily be made up if you can keep from making mistakes further into the stage.