If, like me, you find yourself in the "Other" passport queues at London airports, they can be long and frustrating at the end of long journey. IRIS is available to some expatriates who are not UK/EU citizens, and can save a lot of time. Short queues or queue, and no landing card required. Initially registering can be awkward: not all London airport terminal have registration offices, and they are often not open at the advertised times due to "staff shortages". It is well worth persisting.