Topical today with the extreme heat but I believe we need a rethink on these modern sealed units. I’ve seen video today of very distressed passengers with young children in locked carriages unable to get out. Awful viewing and how long before there are fatalities. To be able to pull a window down just a few inches makes me feel so much more comfortable - am I alone? Last winter I was on a Richmond to Waterloo semi fast and it was so hot, crowded and claustrophobic standing up I simply had to get off at Clapham to get fresh air and the next slow train. A few months ago we made an unscheduled stop at Vauxhall no information as to why we stopped over the tannoy for about 10 minutes. The train was packed and the air con so poor but it was about 15 -20 minutes before we were able to open the doors and get off. Felt like a lifetime for a lot of people on that train. Awful and must put some off travelling by train.