“Applications for extensions of time limits of various kinds are commonplace and the approach to be adopted is well established. As a general rule, when a court or tribunal is asked to extend a relevant time limit, the court or tribunal asks itself the following questions: (1) what is the purpose of the time limit? (2) how long was the delay? (3) is there a good explanation for the delay? (4) what will be the consequences for the parties of an extension of time? and (5) what will be the consequences for the parties of a refusal to extend time. The court or tribunal then makes its decision in the light of the answers to those questions.”