Two years ago a chap met a similar fate whilst travelling on the Gatwick Express. A couple of months ago the train operator was fined £1m.
https://www.bbc.co.uk/news/uk-england-49016151
It is identical to the case cited here. A court ruled it was the operator's fault for not making clear that leaning from a moving train window can result in decapitation. There is, however, slightly more to this story. The gentleman in question was a lifelong rail enthusiast who was working in the industry at the time of his death. He was also a volunteer on a Heritage Steam Railway (of which I am a Life member). With or without warning stickers he should have been aware of the danger. But there is more to come. The Ofiice of Rail and Road's Director of safety Ian Prosser, who is also HM Chief Inspector of Railways, said he had written "to operators instructing them to take immediate action to prevent a similar tragedy happening again". This has serious consequences for Heritage Railways. Almost all of their rolling stock is fitted with the type of "droplight" opening windows featured in the tragedy. They face either retaining them and providing out of character stickers (still running the risk that one of their passengers' idiocy will see them face a crippling law suit) or locking them out of use or providing protective bars. Such railways go to great lengths to achieve authenticity for the periods they represent and a number of them provide period filming facilities. Modifying their stock will cause ridicule when, say, Hercules Poirot and Captain Hastings are seen in a train with metal bars across its windows. And all because a small number of people seem not to retain the sense they were born with.