reg 99C Power to vary sentence
(1) The court may vary or rescind the original sentence if it appears to the court that it had no power to impose the original sentence. (2) The power conferred by this rule— (a) may be exercised within the period of 56 days beginning with the day on which the original sentence was imposed; (b) may not be exercised in relation to any sentence if an appeal, or an application for leave to appeal, against the sentence has been determined. (3) Unless the court otherwise orders, a varied sentence takes effect from the beginning of the day on which the original sentence was imposed.