I agree that this is a likely explanation of what happened, but I don't think it's clear that the mother was instructed by the trolley person to go to another door.
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You obviously haven't read the report
"It was a nice family day out, we'd done a little bit of shopping as well with my friend and her 10-year-old son. We got the train from Cardiff to Gowerton, and my daughter saw a friend sitting a few rows behind us, so went to talk to them. As we were approaching Gowerton, I said to my daughter to come to me so we could get off together."
But a food trolley was blocking the aisle, cutting her off from her daughter.
"I asked if the man could move the trolley so she could come through,
and he said no, and told us we'd have to use different exits," claimed Miss Richards, of Glan yr Afon, Bryngwyn Village, Gorseinon.
"We used different exits, and as we were pressing the buttons to get off at our exit, they wouldn't open. We then squeezed past the trolley to try the other doors, when the train started moving."
Now not all customers can be relied on to tell the truth but it strikes me that something went one here which was avoidable by the TOC or its food franchiser
I am not suggesting the guard goes along checking all the doors, but there was a person on the ground that was aware of the situation allegedly and did nothing. It seems to me that in this occasion, the trolley service was severely lacking in customer satisfaction skills and like it or not, it is still perceived as part of the train crew by Joe Public
It seems some of you on here have a very arrogant attitude to your customers and Joe public and that the railway is always correct and the passengers at fault be it cases like this or ticket irregularities or car / truck drivers at LCs.
I am sure there are plenty who do try it on with tickets or get confused about opening the doors at stations but that doesn't excuse situations like this.
The obvious lesson from here is to keep the coaches clear of obstruction on approach to stations, which some on another thread about trolleys say is the norm on their routes, and TBH on our line to Leicester from Oakham with cross country, I haven't had an issue with the catering trolley although it is usually so full of standing PAX that the trolley cannot be used