Cranshaw’s assaults sent shockwaves and disgust through the community and sparked a major police investigation over a four-year-period.

Detectives wrote to families warning them of the danger to children and headteachers held special assemblies about personal safety.

When police published a CCTV image of a suspect in early 2010, at least two innocent men were questioned after well-intentioned but incorrect tip-offs, police sources said at the time.Detectives finally got their man after receiving intelligence from members of the public and they also linked Cranshaw to a completely unrelated crime.

Cranshaw was found to have helped a friend get revenge on his ex-partner by smearing dog waste on her car in Bury in September, 2010, and was given a 12-month conditional discharge at Bury Magistrates Court.

In March this year, officers arrested him at a house in Didsbury and searched his Whitefield house.

They found a video camera containing nine videos, lasting between 30 and 60 seconds, which, Bolton Crown Court heard, Cranshaw had filmed from his house.

The videos featured young girls walking along the road and they would zoom in on the girls’ legs and bottoms. Cranshaw’s mobile phone contained images — taken from about 10ft away — of different occasions when he had followed schoolgirls aged about 13 or 14, the court heard.

During a police interview, Cranshaw admitted he would store the semen in an empty deodorant bottle and flick it at the girls.

After the hearing, Det Chief Insp Sara Wallwork, of Bury police, said: “Naturally, this incident caused a lot of concern in the community and while speculation started to build, officers in the neighbourhood team had to work hard to offer reassurance on the ground, including working with parents and schools. At the same time, detectives launched a thorough investigation.

“Despite their inquiries, it was still not clear who was responsible, so no suspect was identified. What Dale Cranshaw did was not only bizarre, it was also disgusting.

“We have always worked hard to make the people of Whitefield feel safe, but during two separate periods, we had to work even harder. When we were confident we were looking for one man, we built a comprehensive strategy to work with the public.

“We therefore went back to local schools, issued public appeals and were well placed to act quickly on any new information that came in. The two main officers on this case worked with great passion and drive to find the man responsible.”