Three passengers who physically removed a flasher from a Tube train will not face charges following a year-long police probe.
The group reportedly forced the man off a District line train at East Ham in August last year after he refused to pull up his trousers and swore at them.
Footage at the time showed the man refusing to pull up his trousers while shouting "f*** off* to those who confronted him.
The man was detained under the Mental Health Act.
British Transport Police (BTP) opened an investigation into what it described as an "assault by a number of passengers".
BTP defended its decision to interview the three under caution on suspicion of affray, saying the "extremely vulnerable" man was having a mental health crisis.
Police sent its file of evidence to the Crown Prosecution Service (CPS).
A CPS spokesperson said: "After careful consideration of the available evidence in this case, we concluded there was no realistic prospect of conviction. No further action will be taken."
Assistant Chief Constable Charlie Doyle said: "It is irresponsible to suggest that anybody has a duty to behave like this, particularly towards an extremely vulnerable person suffering significant mental health crisis."
"While charges to CPS weren't successful in this case, it is right that a criminal investigation took place and we will not hesitate to pursue prosecution for those who choose to act in such a way in future."
