'I investigated case of baby boy garrotted and hidden under floor - the mystery haunts me'

When a builder renovating a flat lifted a floorboard, he uncovered a horror that had lain hidden for 114 years. Here, the detective who led the extraordinary investigation into 'Baby Auckland' tells how modern forensics and historical census records cast light upon a century-old homicide - and why he'll never forget the tiny boy buried in a white coffin