Hugo agreed to drive Laurence to Cardiff.  Laurence asked Hugo to drive 5 miles per hour lower than the speed limit. In return, Laurence agreed to pay Hugo an additional £100. At the conclusion of the journey, Laurence refused to pay the extra £100. Hugo then took Laurence to small claims court.

[a] To resolve the matter whether the extra £100 is due and payable, which legal rule will the judge have to apply? Identify that rule.

[b] In apply that rule, what will be the case outcome. Explain using appropriate legal theory derived from that rule.  

[c] Would your answer change if on the day of the journey, the UK authorities issued a travel advisory mandating that all motorists drive 10 miles per hour slower than the speed limit.