Dialogue scenes were filmed twice, in English and then in Welsh; the show was broadcast in both languages. While the dialogue in both versions essentially share the same content, the Welsh scenes were often accomplished with fewer words.
The police station in the series is the former Queens Hotel in Aberystwyth. After being closed as a hotel, it was actually used as the town's police station up until the mid 1990s. However, the entrance used in the series was on the other side of the building.
The production took place in Aberystwyth, Ceredigion, Wales, and the three series were filmed in and around the town, often in rural locations.
For the first series, the historic council building was used as the external facade of the series' fictional police station. During the filming of series 1 the unused building was utilized as the TV production offices, and some scenes were filmed in limited interior areas. Due to the building's sale, interior access for the second series, which was to be filmed starting in September 2014 was denied due to active construction. The exterior continued to be used as the facade of the fictional police station but due to construction, the building interior was unavailable. So anyone watching future series will see people using the steps to the station, but no one is ever seen actually entering the building after series 1.
The first series was shot over a 124-day period in and around Aberystwyth and the surrounding countryside.