During his visit to Windsor, Trump patted King Charles III on the back

During his visit to Windsor, Trump patted King Charles III on the back. Touching the monarch of the United Kingdom is considered a serious breach of royal etiquette. According to established rules, it is not customary to touch the king without his initiative. The exception is a handshake if the monarch himself extends his hand. In other cases, it is considered proper to limit oneself to a slight bow or nod of the head. Source: Global News (EU, USA)