I agree, Perth has always seemed sparkling clean compared to most cities in the UK. Other Australian cities I've visited seemed that way as well.

I think partly it's the light - it's so bright here in Aus that things look cleaner anyway, but also the light and the heat keep things a little cleaner, UV sterilises and the sun bleaches after all.

Aus doesn't have as much of a legacy of concrete brutalism, either, lumpen concrete buildings in the UK that started out grey and end up brown, water-stained from all the rain and oppressive-looking.

And also I think better care is taken. Visiting London after having lived here in Perth for a couple of years about ten years back, I was struck by just how often as I walked around my nostrils were assaulted by smells of rotting rubbish or just plain urine.

So yeah, bunch of things, but it does feel much cleaner here.

Interesting, yes, the UV bleaching things might be a factor.

You are right about the smell of urine and pot in London.