illy ▁Circ us , ▁between ▁ 1 9 1 5 ▁and ▁ 2 0 0 6 . ▁It ▁was ▁designated ▁as ▁a ▁Gra de ▁II ▁listed ▁building ▁by ▁English ▁Heritage ▁in ▁ 2 0 0 4 . ▁ ▁History ▁In ▁ 1 9 1 2 , ▁J ▁Ly ons ▁& ▁Co ▁bought ▁the ▁un used ▁property ▁on ▁the ▁outer ▁edge ▁of ▁the ▁Qu adr ant ▁in ▁Reg ent ▁Street . ▁There ▁they ▁built ▁a ▁hotel ▁called ▁the ▁Reg ent ▁Palace , ▁which ▁opened ▁on ▁ 2 6 ▁May ▁ 1 9 1 5 . ▁It ▁took ▁up ▁the ▁complete ▁tri angular ▁block ▁formed ▁by ▁G lass house , ▁Bre wer ▁and ▁Sher wood ▁Stre ets ▁and ▁rose ▁nine ▁flo ors ▁high . ▁There ▁was ▁also ▁a ▁bas ement ▁and ▁sub - bas ement . ▁It ▁contained ▁ 1 , 0 2 8 ▁bed rooms , ▁but ▁even ▁in ▁its ▁later ▁years ▁had ▁only ▁commun al ▁bath rooms ▁and ▁to ile ts . ▁When ▁opened ▁in ▁ 1 9 1 5 , ▁it ▁was ▁the ▁largest ▁hotel ▁in ▁Europe . ▁ ▁The ▁English ▁architect ▁Oliver ▁Per cy ▁Bernard ▁was ▁the ▁chief ▁designer ▁of ▁the ▁hotel ' s ▁interior , ▁having ▁been ▁en list ed ▁to ▁help ▁by ▁Ly ons ▁in ▁the ▁early ▁ 1 9 3 0 s . ▁Historic ▁England , ▁in ▁ 2 0 0 4 , ▁considered ▁the ▁interior ▁of ▁the ▁hotel ▁to ▁be ▁one ▁of ▁the ▁most ▁important ▁features ▁of ▁the ▁building . ▁The ▁entrance ▁to ▁the ▁hotel ▁was ▁later