“An appeal to the tribunal is a full merits appeal and, in considering the appeal, the tribunal is entitled to substitute its own decision for that of the Commissioner. In a judicial review, the High Court cannot review the merits of a decision but it can merely determine if the correct decision making process has been followed, and if it hasn't the High Court may remit the matter to the Information Commissioner for a redetermination. Even if a judicial review were successful and the Information Commissioner were to issue an adverse decision notice, the full merits of the matter would still ultimately end up before the First-tier tribunal, but with great delay and great additional costs to all sides. It would therefore be far more expeditious and in the interests of the efficient administration of justice for the First-tier tribunal to grapple the substantive merits of the dispute at the earliest available opportunity.”