Although the design museum does superior sandwich and cakes, clearly you may actually be in a different part of town nd need another option. Pret is good value, fresh food with a wide variety of options, particularly for veggies with their veggie special each week. I particularly recommend the egg mayo and roasted tomato baguette or the posh cheddar and pickle. The cakes are not so good though, small and wrapped in plastic. The coffee is good, though not as good as at the design museum but is the best chain place for lunch when generally roaming around london.