What it is
The shape is not decoration. A rounded, smooth-sided aluminium shell has far less wind resistance than a boxy caravan, which means a calmer ride, less sway and better fuel economy on long runs — which is why this shape has stayed in production since the 1930s and why British owners still seek it out.
Why people choose it
Durability is the other reason people buy one. A riveted aluminium skin does not rot the way timber-cored sidewalls do, so a well-kept twenty-year-old unit can still be structurally sound.
What to check before you buy
The compromises: the interior layout rarely changes between models, repair parts are model-specific, and the rounded profile wastes floor area at both ends.