Sculptor John Maine puts years on brand new Green Park Underground station

The gleaming, new stone walls of a ramp out of Green Park station will give visitors some idea how the recently rebuilt above ground buildings might have looked.

There's nothing wrong with them. They are clean and hard-edged. But new work by Royal Academician John Maine looks, by contrast, weathered. Worm-eaten would not be too strong a word. And many rushing past may not even notice it.

The Portland stone which Maine has used to clad the station infrastructure here in Picadilly is ubiquitous. You see it across the road, in the façades of the showrooms and plush residencies of the West End.

But there is more to this material than meets the eye. Maine has worked with blocks of the limestone dating back 150 million years. Most of those pock marks are not artistic intervention but genuine fossils.

This leads to a certain paradox. A brand new central London station ready in time for the 2012 Olympics now wears a look of the Jurassic era. A pattern on the granite floor tiles which spread between the buildings offers to swirl the viewer back in time.

So now waiting for someone outside the station, for no matter how long, may seem like a the blink of a cosmic eye. The new station should delight anyone who stops to take it in. One hopes it might even slow down those rush hour crowds.

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