(1) A deciding officer may at any time -

(a) revise any decision of a deciding officer -

(i) where it appears to him or her that the decision was erroneous -

(I) in the light of new evidence or new facts which have been brought to his or her notice since the date on which the decision was given, or

(II) by reason of some mistake having been made in relation to the law or the facts,

or

(ii) where -

(I) the effect of the decision was to entitle a person to any benefit within the meaning of section 240, and

(II) it appears to the deciding officer that there has been any relevant change of circumstances which has come to notice since that decision was given,

or

(b) revise any decision of an appeals officer where -

(i) the effect of the decision of the appeals officer was to entitle a person to any benefit within the meaning of section 240, and