▁Lyon ▁joined ▁the ▁office , ▁and ▁the ▁firm ▁maintained ▁a ▁busy ▁practice ▁on ▁large ▁scale ▁projects . ▁ ▁They ▁sometimes ▁documented ▁designs ▁by ▁other ▁architect s , ▁for ▁instance , ▁continu ing ▁their ▁hotel ▁work , ▁the ▁design ▁by ▁US ▁architect s ▁Wel ton ▁Beck ett ▁for ▁the ▁Southern ▁Cross ▁Hotel ▁in ▁Bour ke ▁Street ▁in ▁ 1 9 6 3 ▁( dem ▁ 2 0 0 4 ), ▁then ▁the ▁most ▁gl amour ous ▁and ▁up ▁to ▁date ▁hotel ▁in ▁Melbourne . ▁Per rott ▁Senior ▁retired ▁in ▁ 1 9 6 6 ▁in ▁favour ▁of ▁his ▁son , ▁when ▁they ▁were ▁already ▁working ▁ ▁the ▁firm ' s ▁most ▁controvers ial ▁design , ▁the ▁Prin ces ▁Gate ▁Tow ers ▁in ▁Fl ind ers ▁Street ▁in ▁ 1 9 6 6 - 6 7 , ▁known ▁as ▁the ▁Gas ▁& ▁F uel ▁buildings ▁( dem ol ished ▁ 1 9 9 6 ). ▁They ▁also ▁took ▁on ▁town ▁planning ▁projects ▁as ▁the ▁M MB W ▁gradually ▁rel in qu ished ▁powers ▁to ▁local ▁Coun c ils ; ▁in ▁ 1 9 6 9 ▁the ▁firm ▁was ▁appointed ▁to ▁produce ▁a ▁town ▁plan ▁for ▁the ▁City ▁of ▁Pra h ran . ▁In ▁the ▁early ▁ 1 9 6 0 s , ▁the ▁firm ▁was ▁engaged ▁to ▁investigate ▁sl um ▁clear ance ▁in ▁Carl ton ▁for ▁the ▁H ous ing ▁Commission ▁of ▁Victoria ▁- ▁known ▁as ▁the ▁' Per rott ▁Report ' ▁( 1 9 6 5 ) ▁it ▁recommended ▁large ▁scale ▁urban ▁renew al