This beetle turned up in my porch. It looked similar to Carabus nemoralis in my Collins Insects guide but google tells me that this species is generally absent from Wales. I sent photos to the Invertebrate Recorder and he says that it appears to be Carabus monilis - the Necklace Ground Beetle. I am grateful to the UK Beetle site for the following:
"In the UK it is widespread and was formerly common across southern England and the midlands, becoming more local and rare in Wales and further north to the Lake District, but there has been a drastic decrease in recent decades and it is now very local and generally rare, being lost from many of its former sites and now classified as endangered." (From www.ukbeetles.co.uk)
