BOAC I'd have thought, as they were the only airline in 1954-5 in Europe using the Argonaut (and that was also its BOAC class name). Were they still using Yorks in 1954-5 for passenger work/trooping; or had they already relegated them to freight only?
I base all the above on what I've read over the years, because if you'll take a look at my age to the left, you'll see I definitely wasn't around in 1954-5!