23:25Áit is AnsaEpisode 9BBC Two Northern Ireland Duration: 5 minutes Mon 19th Jul 2010, 23:25 on BBC Two Northern IrelandRadio Ulster presenter Brian Mullen takes a nostalgic stroll along Derry's walls.ContributorsProducer:Brid MaloneyDirector:Mal MarkenGenresFactualHistorySeriesÁit is Ansa Source: BBC Online