3. Where a person to whom paragraph 2 applies has immediately before the appointed day been detained in a Borstal institution for less than twelve months, the Secretary of State may at any time after the appointed day discharge that person from the young offenders centre and on such discharge that person's sentence shall expire; and for the purposes of Article 3 of the Treatment of Offenders (Northern Ireland) Order 1976 [1976 NI 4] such person shall be deemed to have been discharged in pursuance of prison rules.N.I.