I bought a super saver ticket for the 11.12 train from London Bridge to Brighton. The ticket said Thameslink only. When I got to London Bridge there was a 10.42 on platform 11 which was a Thameslink train. I waited for the 11.12 to come up. Sure enough it appeared on Platform 12 BUT this was a Southern train. It was the same time and arrived at the same time in Brighton. There was no Thameslink 11.12 train. I wondered if there were other platforms in London Bridge where there were Thameslink trains but there was certainly no signs to these. I also thought that it was highly unlikely there was a Southern train and a Thameslink train leaving LB and arriving at Brighton at exactly the same time. Can anyone throw any light on this. Would I have been fined for being on the Southern train with a Thameslink only ticket? I have searched the net for answers but they don't seem obvious. The Train Line who sold me the ticket are no use at all on the matter.