Lord Goff said that if, at the end of the day, there remained a substantial question of fact or law or both, arising on the facts disclosed by the affidavits, which the plaintiff bona fide desired to try, the court should, as a rule, allow the service of the writ. The standard of proof in respect of the cause of action could broadly be stated to be whether, on the affidavit evidence before the court, there was a serious question to be tried