I was in school doing A level zoology and the class went to Dale Fort in Pembrokeshire in the summer of 1964. John Barrett ( Warden of Dale Fort) welcomed us and entertained us with marine sagas before handing us over to one of his colleagues. John looked in on our progress as the week proceeded, and commented on our findings. He was firm yet genial and hugely knowledgeable. For me, that course at Dale was a career-forming turning point. A childhood of experiences messing round in the rock pools suddenly made sense and fell into a logical framework.