No sooner does the sun finally hit this shivering land than the sneers start flying. I got on the bus the other day, going from the sort of light that shows up the dirt on window-panes to that pond-like gloom familiar on public transport. I forgot to remove my sunspecs. Two girls were watching me. I tried to ignore them. Finally one spoke up. "Who does she think she is?" she said. "Stevie Wonder?"

If God had meant us to walk around with tinted glass on our noses, he wouldn't have invented trees. Sun glare has a function, which is to make us get out of the sun at noon. The human eye is perfectly well adjusted to cope with all but the most unrelenting desert light. We don't need sunglasses.

But our egos do. The thing about sunglasses is that they have two roles beyond sheltering the pupil - self-protection and status. The theory runs that you can stare at other people and they won't notice. This is arrant nonsense. The human animal is still sufficiently highly-tuned to know perfectly well that it's being watched. Pop stars claim sunglasses help them avoid meeting the eyes of the public. Pull the other one. Wearing sunglasses is like wearing a big sign around your neck saying "look at me! I'm a pop star!"

Which is why pop stars manque wander the streets of Portobello in them: they hope someone will think they're someone interesting, someone with standing in the world. Someone with money to squander on accessories. How else do you explain the Ray-Ban phenomenon? When they could walk into Boots and come away with a perfectly adequate piece of eye protection for between pounds 9.99 and pounds 26.50, why would anyone in their right mind go to the Sunglasses Hut and lay out between pounds 79 and pounds 120?

Although Police specs (designed to make you look like an LA motorbike cop and retailing around pounds 100) are gaining in popularity, the Ray-Ban is still the only spec for the desperate-to-impress. One hears a lot about resilience and UVA filters, but our weak northern light is never going to send anyone blind. People buy these icons purely to be able to say "Oh, no; I've lost my Ray-Bans" in public places. Because "Oh, no, I've lost the sunglasses I bought for pounds 2.50 from the man with the felt board outside the station" just doesn't sound the same, does it?

Serena Mackesy