The driver of a high speed train has been sacked for taking pictures of himself, allegedly naked, in his cab on the Sheffield to London route.
The sacked driver used his phone in the train's cab
British Transport Police were called in after officials at Midland Mainline trains were made aware of the incident.
Midland said the man had been dismissed for breaching safety policy, but would not comment on his state of dress.
British Transport Police passed a file to the Crown Prosecution Service which decided not to take further action.
Midland Mainline told BBC News the incident had been reported to them within the last month.
A spokeswoman said: "We did receive an allegation about a driver, and because it was related to a safety matter an investigation was conducted involving British Transport Police and he was subsequently dismissed."
The police statement said: "British Transport Police have conducted an inquiry, a file was submitted to the Crown Prosecution Service who decided it was not in the public interest to proceed."
A spokeswoman for the train drivers' union Aslef said no one was available for comment.