I am going out to walk along part of the Severn estuary with Antony Lyons today to look at potential material for a film we are making on transgression (in the geological sense). This fits into Antony’s on-going work around water, climate change and sea levels, and the whole issue of time and change, ecologically speaking. Walking and talking is also always a good means of reflecting on, sifting through, and generally sharing and digesting thinking material. Today’s trip has a particular feel to it because my friend the artist David Walker-Barker has just agreed to send me a clip of something that provided perhaps the most extraordinary experience of the complexity of geological time I’ve every had. While we were talking in his studio in Yorkshire one evening, David handed me a very large quartz crystal and told me to watch it carefully as I tipped it from side to side. Almost miraculously, as I did so I saw a small bubble of gas move in its liquid heart, much like the bubble in a spirit level. The paradoxical tension between the age and solidity of the crystal and that movement has always remained with me, as mysterious as the viral matter – inert but with the latent potential for life – that makes up part of the DNA of every human being.