I I travelled on the Sealink service in 1984 on the St Nicholas and then carried on from the Hoek on the Moscow train getting off in Utrecht. It was not possible to get on in the Russian carriages as these were sealed on departure until arriving in Poland. I Gather the smuggling activities were legendary with all sorts of Western goods arriving on this service. The Manchester to Harwich service that you refer to was poorly used because it was not shown in the timetable. The BBC one program that’s life featured this service to highlight the absurdity of running the empty train. In 1988 My family was scheduled to take this train getting on in Milton Keynes Central. Unfortunately Sealink went on strike that very day forcing us to change our plans hastily to sail via the Olau line which to be fair had much better ships that even included a swimming pool at the bottom of the ship.