I’m going with 1954, the most modern cars I saw were a Hillman Husky, curved windshield Morris Minors and curved window Ford 100Es. there was also a Ford Consul with curved glass, but I think they got that in 52 or 53
Curved screen Minor 1000 was introduced in 56.
From 53 to 55 it was the split screen Mk2
Got a horizontal slat grill in 54