Britain's railway system thought over as a safe way to travel, transformed into a dangerous

hunting ground for two of the country's most notorious criminals during the 1980s.

John Duffy and David Mulcahy spread terror across London's rail network.

Their reign of violence lasted five years and reshaped British policing permanently. Their case brought

several groundbreaking changes to British criminal investigations. UK authorities used psychological

profiling for the first time, implemented the Holmes computer system and made major

breakthroughs in DNA evidence collection. The childhood friends turned brutal criminals formed a partnership that eventually fell apart,

which led to one of British criminal history's most complex and time-consuming investigations.

This is Monsters.

Music Thank you. John Francis Duffy was born on November 29, 1958, in Dundock, north of Dublin, Ireland, just south of the border with Northern Ireland.

He was the oldest of three children born to Frank and Philomena Duffy.

They were considered a good working class family and Frank worked as a bricklayer.

In his youth, people described John as very polite and that his family was the nicest of people.

When Frank was laid off in 1965, the family moved to the Demarrier House flats on

Lawn Road, just a few blocks away from the North London Rail line.

He was there that John would start attending Haverstock School in 1970.

He was considered a rough school at the time, and since John was short and scrawny, he was

easily targeted by bullies. He was ridiculed over his red hair, so he began wearing a parko

with the hood up at all times, no matter the weather. David John Mulcahy was born on May 23,

1959, and it's known that his parents had immigrated to London from Ireland, but I couldn't

find any information about David's place of birth. David was also the victim of bullying, but he was

bigger and more confident than John. He wasn't long before they realized that they were safer staying

...