Once upon a time, coffee - just a tad more extravagant than humble tea - was the preserve of special occasions in the bustling college canteen. Oh, how we'd savour those moments. On winding train journeys, an entrepreneurial hawker might glide by, proffering what he called 'chaffee': an alchemy of tea laced with a dash of instant coffee. It was pure, unadulterated umami, a wickedly grown-up thrill.