Coroner Dr Fiona Wilcox revealed the extent of the police investigation into the death of MI6 agent Gareth Williams, while delivering a narrative verdict.
Police interviewed more than 200 witnesses.
110 CCTV clips were collected.
300 house to house inquiries were conducted.
Whatever the coroner's verdict today at the inquest into the death of MI6 spy Gareth Williams, many questions will remain unanswered.
Last day of the inquest into the death of Gareth Williams
Experts can't rule out the possibility that the MI6 spy found dead in a bag, locked himself in unaided, before dying.