Recently I went to London for 20 days course at the delhi Airport I was waiting to board the plane in meantime I saw Local international sim counter. Got uk sim for 200rs. With every day data free and call back to india is approx 1rs.
They just asked for passport copy.
As soon as I landed at the airport I called my mother and updated her that I have landed. Good I have bought sim from delhi as the London airport is too big to locate sim card counter.
Throughout my tenure sim worked fine.