▁Western - set ▁films , ▁such ▁as ▁A ▁F ist ful ▁of ▁D oll ars . ▁Fil ming ▁the ▁episode ▁in ▁Spain ▁was ▁che aper ▁than ▁construct ing ▁a ▁set ▁in ▁the ▁UK . ▁M off at ▁stated , ▁" We ▁knew ▁from ▁the ▁start ▁we ▁need ▁some ▁serious ▁location ▁shooting ▁for ▁this ▁one , ▁and ▁given ▁the ▁most ▁icon ic ▁American ▁setting ▁imag in able , ▁there ▁was ▁only ▁one ▁place ▁to ▁go   – ▁Spain ." ▁They ▁reported ly ▁fil med ▁there ▁from ▁ 8 ▁March ▁to ▁ 1 7 ▁March ▁ 2 0 1 2 . ▁Fil ming ▁took ▁place ▁at ▁O as ys / M ini ▁Hollywood , ▁and ▁Fort ▁Bra vo / Tex as ▁Hollywood . ▁While ▁Smith ▁was ▁allowed ▁to ▁try ▁r iding ▁the ▁horse , ▁most ▁of ▁the ▁action ▁shown ▁in ▁the ▁episode ▁was ▁done ▁by ▁his ▁st unt man . ▁Compos er ▁Murray ▁Gold ▁m im icked ▁Western - style ▁scores ▁when ▁creating ▁the ▁music ▁for ▁the ▁episode . ▁ ▁Th emes ▁ ▁James ▁F . ▁Mc Gr ath ▁of ▁the ▁religious ▁website ▁Pat he os ▁found ▁that ▁" A ▁Town ▁Cal led ▁Mer cy " ▁had ▁strong ▁religious ▁them es ▁and ▁moral ▁messages , ▁writing ▁that ▁it ▁" re ally ▁is ▁about ▁mer cy , ▁about ▁forg iveness , ▁about ▁war ▁cr imes , ▁about ▁ven ge ance , ▁and ▁about ▁justice ". ▁He ▁interpreted ▁Amy ' s ▁comment ▁about ▁how ▁the ▁Doctor ' s ▁behaviour ▁was ▁due ▁to ▁his ▁being ▁alone ▁for ▁too