Aired Monday 8 June, 1:30am - 2:00amon BBC News

On The Front Line

The Train Police: Tracking the Sex Offenders

Reports of sexual assault and harassment on trains and at stations are on the rise, but victims say CCTV cameras are often broken or of such poor quality that their attackers can't be identified. We follow British Transport Police officers and staff as they race against time to gather the crucial evidence they need to bring offenders to justice.