Thiru Kumar’s dosas in Washington Square typify the regional cuisine available to New Yorkers – but not Londoners

Why are Indian restaurants in London so awful? I ponder this every time I emerge from one having abandoned a half-eaten plate of greasy dal and a mound of chewy paneer. It can’t be, as free marketeers would claim, from lack of competition. There are hundreds of these places in the city and more than 9,000 in Britain, employing tens of thousands of people. Chicken tikka masala, we are told, has replaced fish and chips as the national dish. We hear about a culinary revolution in London in the past decade. So why do the city’s Indian restaurants pose such a risk to both the palate and the digestive system?