A BYSTANDER has described the moment he witnessed a sexual deviant masturbating in a packed carriage full of women and children.

Repeat offender, Justin McCarthy, was jailed for 21 months for exposing and touching himself on the London rail network.

On six separate occasions between February and March, the 37-year-old homeless man boarded a train and sat next to a woman before touching himself under his clothing.

He would stare at the woman and attract their attention by tapping their legs with his feet if they attempted to look away.

McCarthy was also in breach of a suspended sentence and has served 16 weeks in prison.

Following McCarthy’s sentencing at Blackfriars Crown Court on Tuesday (April 25), British Transport Police has said how a man’s witness report helped them bring McCarthy to justice.

The witness, who wishes to remain anonymous, intervened on August 8, 2016, when he saw McCarthy trying to talk to a woman while touching himself on an eastbound Central line train.

He said: “I got onto an eastbound Central line train travelling home after work. I managed to get a seat opposite a woman on a busy carriage with a mix of commuters and tourists.

“Somewhere between Leyton and Wanstead, something drew my attention to the young man sat next to the woman.

“He was slouched back with his legs spread and I noticed that he had one hand inside the waistband of his jeans and was masturbating. At first I doubted what I was seeing, but then the man leaned over towards the woman and began whispering into her ear.

“She immediately stared straight ahead looking horrified, I made eye contact and stood up to give her my seat. I then stood between the man and the woman to block his view of her.

“There were other women and children on the train and I tried to position myself so that I obstructed his view as much as possible.

“I couldn’t believe this was happening and it was a very unpleasant to watch. I then remembered my phone and took it out and took a photo of him, the police later stated this was incredibly useful.

“The man got off at Newbury Park and I decided to follow him to see what direction he walked off in as, by this time, I had decided I would report the incident to the police, which I did so at the nearest Metropolitan Police station.”

British Transport Police investigating officer, PC George James said: “Thankfully all the women reported McCarthy’s behaviour to police and he was eventually arrested and charged for the offences.

“We simply will not tolerate such behaviour and take all reports very seriously. I encourage anyone who experience or witness unwanted sexual behaviour on the rail network to report it to stop it as soon as possible to give us the best chance we can have in catching offenders.”