officers and medical staff "heart" for the medical themes featured regularly in the programme; and "beat" based on the phrase "the bobby's beat" ("bobby" being British slang for a police officer (from Robert Peel)). Each episode's set of storylines were inspired by those created for the Constable series of books, written by Nicholas Rhea (the pen-name of former policeman Peter Walker), which were focused on a police constable in the 1960s who came to Aidensfield, in order to serve the local community and solve crimes that took place on his new patch. Much of the characters and locations in the Constable series were directly used for creating the setting and plots in Heartbeat, under guidance from Rhea. The series was originally intended as a launch platform for actor Nick Berry, following his involvement on the BBC's soap drama EastEnders, who alongside actress Niamh Cusack, were the prominent main actors of the programme for its first two series. Storylines mainly focused around both their characters, as they offered aid to those around the village and beyond, though the tone of plots was portrayed with grittiness and social realism. From the third series onwards, the role of the village policeman continued to be central to the storyline, but supporting actors were redefined as the programme's main cast, with their characters elevated in presence, effectively evolving Heartbeat into an ensemble drama that was themed as more cosy and comfortable compared to more modern TV police dramas. The changes were more notable by how supporting actors gained more prominence in the opening titles after being elevated into the series' main cast up until the fifth series, both Berry and Cusack were prominently featured in the opening credits, but this changed in later series so that by the beginning of the seventh series, all actors in the main cast were given proper credit for their involvement in the drama series. After the fifth series, storylines became less centralized around the village constable, focusing on separate storylines that retained a set structure within episodes: one focusing on a crime solved by the village constable and his colleagues at Ashfordly police; one focused on a medical issue that the village doctor and/or nurse would treat; and a side story focused on the programme's "lovable rogue" character which mainly was designed as comic relief, but sometimes featured light-hearted plots delving into heart-warming moments. In addition, over-arching storylines covering