Hi Jorose, thank you for that information!
The records in relation to Bernheardnia I had seen, but you've picked up on something I'd completely overlooked; that Hubert gave the Hull address as being his father's address too in 1940. I hadn't been able to find any indication at all that Rudolf had ever gone to England.
Although to be honest I do wonder whether it might have been a lie on Hubert's part, to avoid any uncomfortable questions about his heritage. It would seem from other things I've since found that he described his father variously as either Belgian or Austrian; certainly he lived in Austria but I have found a possible baptism which, if it was the right one, would make him German, something which Hubert might have wanted to disguise to enable him to travel as widely as he clearly did. I also kind find a death record for Ruldof in England.
It's fascinating that Hubert did travel so much - I've seen a suggestion that he studied or worked in the field of languages so that is possibly why but I wouldn't be surprised if there was more to the story either.
Thanks again 🙂