Katherine Parkinson: 'I like stuff that's both harrowing and hilarious'
The IT Crowd star, currently tackling Ayckbourn at the National, on why good comedy needs an element of darknessThere are only so many boxy power-suits an actor can wear without itching for a costume change: a corset, a wedding dress, anything.So Katherine Parkinson, four years in shoulder-pads as guileless office manager Jen in Channel 4 sitcom The IT Crowd (and outfitted pretty identically for her role as maitre d'…