2x09 Episode 9
2x10 Episode 10 [series finale]
It's the second -- and very much final -- Romanzo Crimifinale! And these make for a neat two-parter of an ending. In the first, the gang are finally brought to trial, and we see how that pans out for everyone. Then in the second, it's years later and we discover everyone's ultimate fates -- including who the old man was in the pre-titles of series one episode one. Grand.
Yes, Prime Minister 
1x01 Crisis at the Summit
Gold's reboot, from the original writers but with a new cast and set in the present day, and based (in part or whole, I don't know) on the 2010 stage play. It's a little odd, with the characters falling somewhere between impression and re-interpretation, but it is still funny. May just take a bit of time to bed in.
Yes, Prime Minister: Re-elected
A tribute-ish programme to the original and mini behind-the-scenes on the reboot, including interviews with fans, the writers, politicians, Whitehall staff, and so on. Actually very good, aside from the repetitious reminders that there's a new series on Gold, donchaknow.