This flimsy piece of paper is not a ticket, but is a label designed to be attached to items of luggage travelling aboard the famous Golden Arrow train. There is no date on this label so it is difficult to work out whether it is pre- or post-war.
In the days before aircraft the fastest means of travelling between Britain and France was by trains that linked directly to ferries at Calais and Dover. One of the most famous trains was the daily Golden Arrow, transporting passengers from London Victoria to Dover, then by ferry to Calais and onwards to Paris Nord by the French counterpart the Flèche d’Or. The journey took about 6 hours in each direction. Read more here.