3E+WA person sentenced to corrective training or preventive detention in England and Wales who was or ought to have been detained in pursuance of his sentence immediately before the commencement of section 60 of this Act shall be treated for purposes of detention, release, recall and otherwise as having been sentenced to a term of imprisonment of the same length as the term of his original sentence and, if he was originally sentenced to preventive detention, he shall also be so treated as if an extended sentence certificate had been issued in respect of him.