Glen Cullen also from The Thick Of It is a great sadsack character. We get hints that he's quite a lonely man. He's the "irrelevant man" who's a bit older than everyone else nd is not taken seriously. He just looks like a sad teddy bear who wants love but constantly gets shat on (especially by his old pal Hugh in the first few episodes) Did a rewatch of the whole thing recently and was surprised at how Glen gets a lot of the best lines. He may be even my favourite character (along with Jamie and Mannion) His meltdowns in Spinners and Losers and the final ever episode are gold.
He's also responsible for the funniest line, I reckon, in the entire run.
"Have you seen Notting Hill?"
"She's probably fucking in it"