▁market ▁rate ▁of ▁£ 1 0 ▁per ▁a cre . ▁( The ▁first ▁plot ▁bought ▁was ▁ 7 1 ▁acres ▁from ▁the ▁Rev . ▁R . ▁Ross , ▁vic ar ▁of ▁Harm ond sw orth .) ▁The ▁site ▁was ▁bounded ▁to ▁the ▁n ortheast ▁by ▁C ain ' s ▁Lane , ▁to ▁the ▁south ▁by ▁the ▁Duke ▁of ▁North umber land ' s ▁River , ▁and ▁to ▁the ▁west ▁by ▁High ▁Tree ▁Lane . ▁The ▁air field ▁boundaries ▁were ▁south ▁of ▁the ▁Bath ▁Road , ▁north west ▁of ▁the ▁Great ▁South ▁West ▁Road , ▁and ▁about ▁two ▁miles ▁west ▁of ▁the ▁western ▁end ▁of ▁the ▁Great ▁West ▁Road . ▁The ▁air field ▁was ▁about ▁three ▁miles ▁by ▁road ▁from ▁the ▁Hay es ▁factory . ▁▁ 1 9 3 0 s ▁ ▁June ▁ 1 9 3 0 : ▁The ▁air field ▁was ▁declared ▁oper ational . ▁ 1 9 3 0 ▁to ▁ 1 9 3 9 : ▁The ▁air field ▁was ▁first ▁called ▁Harm ond sw orth ▁Aer od rome , ▁then ▁The ▁Great ▁West ▁Aer od rome , ▁and ▁sometimes ▁He ath row ▁Aer od rome . ▁One ▁pre war ▁map ▁labels ▁it ▁" A ir port ". ▁A ▁hang ar ▁was ▁built . ▁F aire y ▁planned ▁to ▁re loc ate ▁its ▁factory ▁at ▁Hay es ▁to ▁the ▁site . ▁The ▁Great ▁West ▁Aer od rome ▁was ▁used ▁for ▁aircraft ▁assembly ▁and ▁testing . ▁Com mer cial ▁traffic ▁used ▁Cro yd on ▁Airport , ▁which ▁was ▁London ' s ▁main