For more than six decades, the eccentric but dedicated Marazzi family, beloved in London’s affordable-travel world, have run budget inns where people from around the world mingle. Few other hoteliers put as much heart into making sure guests are acclimated to London by answering questions, obliging special dietary requests, and filling bellies with a cooked breakfast that’s so enormous (try the banana yogurt) that lunch might become optional. To keep attracting longtime regulars—there are many, going back more than half a century, because the Marazzis owned the departed St Margaret’s Hotel for 56 years—the Celtic, a defiant holdout from the way British hospitality used to be, retains quirkyfeatures: Rooms don’t have TVs or phones, furniture is endearingly mismatched, and the lounge is a hub for socializing with fellow guests. Add up to £22 if you don’t want to share a shower or toilet. You must book directly.