If just finding the immigration records is the point this is not much use, but if, as you say, you would like to know more about their travels I would suggest approaching from a different angle. What did the father do? It was not easy to get away from the UK at that date mostly because of the shortage of shipping due to war losses, but it certainly was not otherwise restricted. If you could find a passage you went. However both Portugal and Leopoldville (Belgian Congo) would have been very unusual places for an Englishman to go to unless he was going to a job, when he would have easily got a passage because the company would arrange it. Elsewhere I think you ask about "Berth" and someone has pointed out that that would be the berth number for the ship. To me this points to someone who was au fait with port activities and shipping and I think you also say something about being a sailor. Skilled seamen also had shore jobs, things like Marine Superintendents, who would be responsible for the running of the port activities like berthing (not very popular to have two ships trying to get into the same berth!!). Leopoldville was a busy port and if you can find where they were in Portugal and that was also a port I think it would support my ideas. Was Kenya mentioned? Mombasa was an important port. I would start trying to trace his employment history if I were you. Just a suggestion. Oh yes, Leopoldville is now Kinshasa capital of the Democratic Republic of the Congo.