His second low budget television film, a short called Reignited was made for Channel 4's Coming Up strand and met with critical success.
[2] In 2003, Catherine Wearing employed Sen to direct Channel 4's £2 million flagship drama Second Generation starring Parminder Nagra.
[10] In November 2021, Sen stepped down as executive producer of EastEnders to lead the fellow BBC continuing drama Casualty.
He received a positive reception for his storylines involving the Carter and Panesar families, as well as reintroducing historical cast member Charlie Brooks as Janine Butcher.
However, he was criticised for various decisions including killing off characters seen as key to the show’s future such as Dennis Rickman Jr, mishandling Chantelle Atkins' (Jess Plummer) abuse storyline by having her abuser Gray Atkins become a serial killer, making long-time character Sharon Watts try to poison her oldest friend-turned husband Ian Beale, breaking up Linda and Mick Carter’s long-term marriage by having Linda start an affair with long-time resident Max Branning, and a lack of aftermath within storylines and introducing incidental music that viewers found to be "jarring".