Maartje Tamboezer, 15, killed on way to sweetshop

Mulcahy, a 41-year-old builder of Chalk Farm, north London, had planned a number of the attacks in the 1980s with his "wicked soulmate", the jury heard.

As youths Duffy and Mulcahy used to go out shooting at people with air rifles.

Their friendship continued after they both got married and used to go out together at weekends.

Giving evidence in Mulcahy's trial, Duffy said: "We would plan it quite meticulously.

"We would have balaclavas and knives. We used to call it hunting. We did it as a bit of a joke. A bit of a game."

In July 1984 the pair raped two girls on Hampstead Heath.

Alison Day was just 19 when she was killed

"We were very excited we had two victims. We thought it was great really," said Duffy.

He said the two men had laughed about the rapes afterwards while listening to Michael Jackson tapes.

In 1985, the pair turned to murder.

Alison Day, was just 19 years old when she was raped and strangled at Hackney Wick station, east London, in December 1985.

The following April, schoolgirl Maartje Tamboezer, 15, was attacked by the men as she went to the shops to buy sweets.

She too was raped and strangled near her home in Horsley, Surrey.

Newly-married Anne Lock, 29, killed in 1986

A month later in May 1986, newly-married TV presenter Anne Lock, 29, was killed by Mulcahy - probably suffocated - as she returned to her home at Brookmans Park, Hertfordshire.

John Duffy, 41, was jailed for life in 1988 for two of the murders but cleared of killing Anne Lock.

He had attacked more than 20 women - most aged between 15 and 32 - at railway stations in and around London and became known as the "railway rapist".

Mulcahy's part in the appalling crimes was only revealed by Duffy while in prison.