ex ▁to ▁win ▁a ▁civil ▁war ▁on ▁his ▁planet , ▁and ▁the ▁Doctor ▁is ▁uns ure ▁of ▁what ▁is ▁the ▁right ▁thing ▁to ▁do . ▁ ▁Show runner ▁Steven ▁M off at ▁pitch ed ▁the ▁Wild ▁West ▁theme ▁to ▁Wh ith ouse ▁when ▁thinking ▁of ▁ways ▁to ▁give ▁each ▁episode ▁a ▁distinct ▁theme . ▁Wh ith ouse ▁further ▁developed ▁the ▁theme , ▁including ▁classic ▁Western ▁trop es ▁and ▁a ▁sympath etic ▁villa in . ▁" A ▁Town ▁Cal led ▁Mer cy " ▁and ▁the ▁previous ▁episode ▁" D in osa urs ▁on ▁a ▁Sp aces hip " ▁were ▁the ▁first ▁to ▁enter ▁production ▁for ▁the ▁sevent h ▁series . ▁Much ▁of ▁the ▁episode ▁was ▁fil med ▁in ▁March ▁ 2 0 1 2 ▁in ▁the ▁desert ▁area ▁of ▁Al mer ía , ▁Spain , ▁in ▁M ini ▁Hollywood ▁and ▁Fort ▁Bra vo , ▁locations ▁used ▁for ▁many ▁Western - set ▁films . ▁Review ers ▁noted ▁that ▁the ▁episode ▁addressed ▁a ▁moral ▁debate . ▁" A ▁Town ▁Cal led ▁Mer cy " ▁was ▁watched ▁by ▁ 8 . 4 2 ▁million ▁view ers ▁in ▁the ▁UK . ▁Crit ical ▁reception ▁was ▁generally ▁positive , ▁with ▁some ▁critical ▁of ▁the ▁Doctor ' s ▁actions ▁and ▁p acing . ▁ ▁Plot ▁ ▁Pre quel ▁A ▁pre quel ▁to ▁" A ▁Town ▁Cal led ▁Mer cy " ▁was ▁released ▁exclus ively ▁onto ▁i T unes , ▁and ▁titled ▁" The ▁M aking ▁of ▁The ▁G uns ling er ". ▁It ▁dep ict s ▁the ▁actual ▁making ▁and