Violet Ground Beetle (Carabus problematicus)
Not to be confused with its far more common look-a-like, the Violet Ground beetle 'Carabus violaceus', this is a quite impressive looking beetle, with this bright metallic purple/violet sheen.
How can you tell the two beetles apart?
Read the accompanying commentary to this video to find out:

Carabus problematicus is a species of beetle endemic to Europe, where it is observed in Andorra, Austria, Belgium, Great Britain, the Czech Republic, mainland Denmark, the Faroe Islands, Finland, mainland France, Germany, Hungary, Iceland, Ireland, mainland Italy, Latvia (doubtful), Liechtenstein, Luxembourg, mainland Norway, Poland, Romania, northern and northwestern Russia, Slovakia, Slovenia, mainland Spain, Sweden, Switzerland, and the Netherlands.