As One Green says, it was a Canadian built (Canadair DC4M North Star) BOAC Argonaut, in this case "Atalanta". I don't know what film clip you saw, but this one in the BBC archive mentions the type more than once and the "wheels-up" seems pretty snappy to me, certainly not noticebly delayed!
BBC - Archive - Princess Elizabeth - News | King and Queen See Royal Departure
The return is detailed in the "Flight Archive" here:
1952 | 0425 | Flight Archive
Details on the Argonaut:
Canadair North Star - Wikipedia, the free encyclopedia
Hope this helps.
TC