2023 January 26, Pip Dunn, “Merseyrail '777s' are OK for commuters”, inRAIL, number988, page60:
As I say, it was a very hot day, and I found that theair-con was better on 777013 than either 777001 or 777009. There are, however, no emergency hopper windows, so if theair-con goes down on a hot day, you will cook!
