Figure caption, The killer was caught on camera filling his car shortly after leaving Michael Mullins for dead

By Jonny Humphries

Reporting from Manchester Minshull Street Crown Court

Warning: This article contains distressing content

One afternoon in April, a children's nursery worker approached her manager in what she described as an hysterical state.

Gabrielle Debotte said she had something serious to tell Nicola Goddard, adding: "You're going to hate me and I'm going to lose my job."

What the 27-year-old said next proved a turning point in the investigation into the death of popular head teacher Michael Mullins, who had been struck by a car the previous day and dragged under its wheels for more than a mile.

Debotte told the astonished Goddard she not only knew who was responsible for hitting the 56-year-old as he cycled home from work, but she witnessed what happened from the passenger seat.

That night, having initially been treated as a suspect, she sat in the interview suite at Stretford Police…