The last time I painted my house’s exterior windows I was in hurry and slopped the paint on, especially on the sills. The result was a wrinkled surface where the drying regime in thick layers of paint had pulled the skin into ridges. It had happened before but this time I noticed something in the patterns. I’d seen them before.

In 1952, Alan Turing wrote a mathematical paper on pattern formation in biology that was for decades regarded as a curiosity and is now acknowledged as a major contribution to morphogenesis, pattern formation in living systems. Purely mathematically, Turing deduced the patterns that would form in reaction-diffusion systems, ie where a chemical diffusing through a medium, meets another chemical, reacting and continuing  to diffuse. The local reaction can change the diffusing pattern at the wave front. Sometimes the product of the reaction can temporarily inhibit the diffusion.

The result is complexity, rather as complexity results from iterative equations in fractals. Turing-type patterns exist in nature, in brain corals for instance.  My paint wrinkles resemble brain coral very closely.  I particular like the bifurcations that appear in these systems. The pomacanthus fish shows this very nicely.

Turing has many illustrious achievements to his name. Now I realise he is also the man who made even watching paint dry interesting.

One of the pleasures of nature watching in your own garden is the yearly weather induced variation and the chance arrivals. Once the season is set it’s often dominated by a particular phenomenon. There was the year blackbirds raised a brood in our hedge – the only time in 25 years this has happened. Two winters ago it was a great horde of greenfinches regularly fighting over the bird feeder. Last year many mint moths suddenly appeared on the wild marjoram.

This year it has been the gatekeeper butterfly.  The hot July gave a boost to butterflies but in North London it seems very few species were left able to take advantage of it. It’s about 5 years since we saw a peacock in the garden. This year, apart the usual early orange tip and a single speckled wood, until July there were a few visits by a comma, a regular in recent years and that was it.

There were plenty of whites around in July as predicted but the gatekeepers have been a constant presence, swelling to a maximum of 5 at the same time on the last very hot day of July. Gatekeepers are not urban butterflies and it seems they were never found in London during the years of industrial pollution. They returned to Hampstead Heath in 1991 and seem to be thriving. They’ve certainly been regulars in our garden for the last few years but never on this scale. So good for the gatekeepers but where are the red admirals that used to swarm over a large buddleia bush in the street two doors away? Where are the peacocks?