Edith and Tom await the arrival of Rose and Mary for lunch at Rules Restaurant in Covent Garden, a couple of days before Rose and Atticus's wedding, spring 1924. Rules (est. 1798) is London's oldest restaurant. Episodes 3.7 (1920), 5.8 (1924) and 6.3 (1925) all contain references to, and scenes filmed at Rules. A bit of trivia: Laura Carmichael appears in all three scenes.