The total cost of our meal, including wine, was £23.80, which is about as cheap as it gets in these parts. The only competitor is Pret A Manger in the basement of the National Gallery opposite, but that's only open after 6pm on Wednesdays, whereas the Café in the Crypt stays open till 8pm every weekday - and later on Thursdays, Fridays and Saturdays, provided there's a concert on upstairs.