Natasha, originally from Liverpool, revealed on Twitter she felt "violated" after a man "rubbed his manhood against her on a train."
She wrote: "This vile excuse of a man just had his penis pushed up against me while on this overground train from London Bridge heading to Elmstead Woods.
"I thought it was a bag until I felt him heavy breathing down my neck. I am appalled and calling the transport police when I get off."
She later told her 162,000 followers: "Honestly I am shaking and feel so violated now. But more than anything I am so angry. This has to stop happening to people."
A British Transport Police spokesman today confirmed the arrest.
They said: "Detectives from British Transport Police recently appealed for information after a man sexually assaulted a woman on board a train between London Bridge and Elmstead Woods.
"The incident happened at approximately 10.47pm on October 10th. In connection with this incident, a 46-year-old man from Wood Green was arrested on suspicion of sexual assault. The man has since been released under police investigation. Further inquiries continue in relation to this incident."
He added: "The media and public are thanked for their help in sharing this appeal."