“The meaning of rule 7.6(3) is plain. The court has power to extend the time for serving the claim form after the period for its service has run out "only if" the stipulated conditions are fulfilled. That means that the court does not have power to do so otherwise. The discretionary power in the rules to extend time periods – rule 3.1(2)(a) - does not apply because of the introductory words. The general words of Rule 3.10 cannot extend to enable the court to do what rule 7.6(3) specifically forbids, nor to extend time when the specific provision of the rules which enables extensions of time specifically does not extend to making this extension of time.”