A man's been arrested at Plymouth railway station after allegedly entering the driver's cab of an overnight sleeper train.
It happened on the London to Penzance service in the early hours of this morning.
Police say it appears to be an isolated incident, rather than any wider threat to the rail network.
A spokeswoman for British Transport Police said: "At this stage, there is no evidence to suggest any threats were made towards the driver or other passengers during the incident.
"The 51-year-old - who is from Canterbury - is currently in police custody where he is being held on suspicion of obstructing the railway."
There has been a big rise in sexual offences on the region's rail network, according to figures out today from the British Transport Police.
There were 55 incidents last year - that's up 33%. But the force says overall crime is down for the eleventh year in a row.
It follows a campaign to target lines with the worst problems and deploy more officers at night and weekends.
British Transport Police are appealing for information after several trains in South Devon have crashed into objects deliberately placed on the railway line.
In the last month, concrete lids, metal road signs and cones have been put on the line near Newton St Cyres. The incidents have led to several delays.
The British Transport Police is warning people to keep an eye on their belongings when they're travelling on trains between London and Cornwall.
Teams of officers have travelled in relay between London Paddington and Penzance on board First Great Western’s 1206hrs departure from Paddington.
They've been offering advice and safety tips as well as handing out leaflets and answering any questions or concerns passengers may have about keeping their possessions safe.
British Transport Police are appealing for witnesses after a high-speed train suffered damage after striking a tyre believed to have been deliberately placed on the line.
It happened last Sunday (22 December) at around 1.20pm.
A train travelling towards Penzance struck the large tyre on the tracks between Menheniot and Liskeard.
British Transport Police said there was an alleged incident at Exeter St David's Railway Station in which three men who refused to buy tickets became verbally abusive to members of staff.
Police have released CCTV images of three men they believe will have information that could assist Officers.
The alleged incident happened at about 4pm on Monday (29 July).
British Transport Police say a train manager suffered abuse on a service between Truro and St Austell.
Officers have now issued the above CCTV image of a woman they would like to speak to in connection with the alleged incident, which took place onboard the 21:45hrs Penzance to London Paddington sleeper service between 10.30pm and 11pm on Friday.
British Transport Police have confirmed that one person has died after a train hit a car on a level crossing in Somerset. It happened near Athelney, which is on the line between Taunton and Castle Cary.
There were no reports of any passengers on the train being injured in the crash.
The car is trapped under the front of the train and services are stopped in the area. First Great Western is operating replacement buses between Taunton and Westbury.