The given words belonging to different parts of speech together make up a 'simple sentence.' The subject(pronoun 'we') followed by the verb('departed') and the two prepositional phrases in a row('for Paris' and 'on a Eurostar train', both functioning as an adverb to modify the action). All these elements together follow the structure of a simple sentence conveying a complete sense both lexically and syntactically. Hence, it is <u>a simple sentence</u>.
