A "very dangerous" serial sex predator was jailed indefinitely today for groping schoolgirls, joggers and women heading home from work.
Michael McCalla, who rode around on a child's bike looking for likely targets, even continued one assault while his horrified victim phoned police.
His year-long campaign - mostly committed on bail for a similar offence - ended after he threw a young student to the floor in a block of flats and "forcefully" abused her.
She fought back tears as she recalled screaming in terror as he tried to strip her from the waist down.
"I couldn't move, kick or anything," she said
Finally, after driving him off with her "high-pitched" screams for help, she staggered to her feet.
A neighbour, disturbed by the commotion, found the "hysterical" woman halfway up a flight of stairs and just yards from the safety of her home.
Her tights had been torn and her knees lacerated.
In a "dramatic" tape recording of her 999 call she could be heard sobbing uncontrollably as she explained how her "black, dreadlocked" attacker first followed her into her block of flats in south London minutes earlier.
He then "pushed me down on the stairs and put his hand up my skirt.
"I just screamed and then he left," she managed to add.
McCalla, 45, was identified shortly after the attack from DNA retrieved from the woman's tights.
He was arrested and subsequently identified by all his victims.
But before he could be brought to trial he was jailed for nine months at Kingston Crown Court for a similar attack.
McCalla, from Clapham, south-west London, who insisted he was the victim of mistaken identity, was subsequently convicted at Inner London Crown Court of eight sexual assaults involving seven victims between 16 October, 2007 and 10 October last year.
The jury failed to reach a verdict on a ninth count.
But in an unusual move, Simon Molyneux, defending - who accepted his "very dangerous" client had carried out "terrifying, frightening and unforgivable attacks - said the defendant had actually "instructed me to tell the court he also committed that offence".
Sentencing, Judge Mervyn Roberts, told McCalla: "You caused considerable and ongoing distress to your victims.
"The number of victims by itself is a serious aggravating feature."
The "most serious" attack was his last, committed after following her home.
"You desisted only because her screaming frightened you and you left. The effect on her was dramatically illustrated when the tape of her call to police was played."
The judge said while McCalla had since shown "a degree of remorse", the fact remained he "represented a considerable danger to women.
"There is a significant risk to the public of serious personal injury of either a physical or psychological nature by the commission by you of further such offences".
For that reason he would be jailed indefinitely.
Although he would have to serve a minimum of two years 148 days before the Parole Board was "entitled" to consider his release, he would not be freed until "you are no longer considered to be a danger".
Even then he would remain on licence for life.
Outside court, Detective Inspector Mark Cranwell said: "The capture and conviction of McCalla will reassure the public that this man had been taken off the streets.
"His offences were becoming increasingly violent and bolder. We are indebted to the victims and witnesses in this case who have come to court and relived their ordeal."
The officer added: "I would like to take this opportunity to assure anyone who believes they may have been a victim of sexual assault by this defendant to report it to the police and we will investigate."
They could ring either Crimestoppers UK on 0800 555 111 or the Sapphire Unit at Wandsworth on 020 8247 7520.
Describing the "unpleasant" attacks, Paul Cavin, prosecuting, said apart from two 14-year-old schoolgirls on their way to lessons, McCalla's female victims were all in their 20s.
He said some of those he assaulted were jogging in the park, out walking their dogs, or on their way home from work.
The barrister told jurors the defendant targeted the schoolgirls after asking them for directions.
"He then put his hand up the skirt of one shocked girl, stepped back and immediately went for the second."
Matters took a "more sinister course" when one women, groped while "limbering up" in a south London park, was attacked by the defendant a second time in the same park four weeks later.
"On this occasion she was jogging when she saw the same man, and tried to call the police on her mobile.
"It was perhaps an escalation in his behaviour because...he came up to her and said 'I know you are calling the police' and yet he still had the nerve to carry out a second assault."
The barrister said McCalla's final attack was the following month.
"Once again there was an escalation in his behaviour."
Taking up the story, the student, speaking from behind screens, said the defendant sneaked up behind her as she opened the communal entrance to the block of flats where she lived and "tailgated" her into the building before the door could close.
"I thought he must have forgotten his key...and just carried on. I got on the first or second step of the stairs and was on the phone to a friend when I remember just being thrown down and this man on my back."
With his weight bearing down on her and her arms pinned to her side there was nothing she could do as he groped her and started to tug at her underwear.
"He didn't say anything to me. I was just screaming 'no'. I was just screaming and screaming."
Seconds after he fled a neighbour came to her help.
McCalla claimed apart from the student all his victims had wrongly identified him.
In a prepared statement he insisted he met her outside a nearby pub after she phoned "wanting to buy some cannabis".
He insisted that after smoking some of the drug, he fondled her, walked her home and then tried to resume his sexual advances.
However, she pushed him away, he pushed her back and she fell over crying. He then tried to comfort her and then left.
But when his account was put to her by Mr Molyneux, the student, who cannot be identified for legal reasons, insisted she did not know McCalla, had never bought or smoked cannabis and had never had any consensual contact with him.Reuse content