Just clarifying for myself, with the aid of Wikipedia, my vague memory of the Chris Langham/Hugh Abbot series. My memory of the later ones is much clearer:
"Series 1 (2005)
In the first batch of three episodes, Hugh Abbot is installed as a new minister following the forced resignation of his predecessor Cliff Lawton. These episodes follow his attempts to make his mark on the department by introducing new policies while following the party line enforced by Malcolm Tucker. Due to a series of complications and mistakes, this leads to the minister coming close to resignation on a number of occasions."
"Series 2 (2005)
The second batch of episodes takes place before a cabinet reshuffle, and follows Hugh's attempts to keep his job. Ollie Reeder is seconded to number 10 "to phone his girlfriend" Emma Messinger, a member of the shadow defence policy team, where he is under the close eye of enforcer Jamie. Meanwhile, Terri Coverley is on compassionate leave following the death of her father, leaving her role to Robyn Murdoch, a senior press officer. The department also has to contend with the interference of the prime minister's "blue skies" adviser Julius Nicholson. The minister and the department survive the reshuffle, with the department being rebranded as the "Department of Social Affairs and Citizenship" and moved to a new building. However, the mistakes and compromises continue."
"Specials (2007)
In the two specials, following the Christmas break, Hugh Abbot is in Australia and the department has to "babysit" junior minister for immigration Ben Swain, who is described as a "Nutter" (a term used for supporters of prime-minister-in-waiting Tom Davis).[14] The first special ("Rise of the Nutters") revolves around a computer problem at Immigration, which is exacerbated by the junior minister appearing in a disastrous Newsnight interview. The opposition policy adviser Emma Messinger capitalises on the error by stealing an idea from her boyfriend Ollie Reeder, to send the shadow minister Peter Mannion on a fact-finding mission at an immigration centre. ...Tucker conspires with Ollie to leak the prime minister's "legacy programme" (the PM's plan to move the handling of immigration policy to a non-political executive board) in the hope of stalling his departure, inadvertently leading the PM to resign early. The next episode ("Spinners and Losers") follows a single night of "spin", as advisers, junior politicians and enforcers all try to better their position during the transition, but only Malcolm gets anywhere."
"Series 3 (2009)
In series 3, Hugh Abbot is replaced as minister by Nicola Murray, played by Rebecca Front. She is an unexpected, last-minute choice for the position, and given her inexperience and lack of staff, she is forced to retain Ollie and Glenn as her advisers. ... With the cloud of the forthcoming general election and tension at 10 Downing Street looming, the series also broadens its scope to include episodes set at the annual party conference and BBC Radio 5 Live. We also see more of Murray's opposite number, Peter Mannion, and other members of the opposition first seen in the 2007 specials. The gradual breakdown of Malcolm Tucker and appearance of new threats to his control, in particular Steve Fleming (David Haig), are also major plotlines. The series ends with Fleming forcing Malcolm's resignation, only to be ousted himself a matter of days later. Having regained dominance, Malcolm decides to call an election immediately to seize the initiative from his enemies in the opposition and his own party."
"Series 4 (2012)
In series 4, the government and opposition have switched places following an election during which JB failed to gain a majority and is therefore in coalition government with a smaller third party. Peter Mannion has been made the Secretary of State for Social Affairs and Citizenship but has to contend with Fergus Williams, his junior partner in the coalition. Meanwhile, following Tom Davis's defeat and resignation, Nicola Murray had been elected by her party, apparently on a technicality over Dan Miller, her opponent, as leader of the opposition, although she resigns at the end of episode four and is replaced by her deputy, Miller. A running thread throughout the series is an ongoing "Leveson-style public inquiry" which takes place in episode six. "