In short, if you can pay by Oyster - your can't drink and ride. Unless of course you're an MP and then apparently you just do it and play down any drama and no fines at all.
So based on experience, other experiences and laws.
Also note many companies run dry-trains, so with that, can't drink or carry(questionable as long as sealed and not been open you can afaik).
https://www.drinkaware.co.uk/alcohol-facts/alcohol-and-the-l...
I know there are specific trains where drinking is banned. Elsewhere in this thread, there are some examples in Wales. I can't find anything about it being banned on trains to Chessington, or anywhere on South Western Railway, though. Not can their help person on Twitter:
Rather than doubling down on your argument, accept you are wrong and move on.
This is wrong. You can pay with an Oyster for Thameslink services out of and through London for example and drink on those. It literally only applies to Tfl operated services.
Had a check on thamelink and darn - lucky you https://twitter.com/tlrailuk/status/1078740639674744834?lang...
Just don't move to the otherside of London if you like a drink.