Discovered this years ago the website states its "free with all London Eye tickets". In fact, you can just walk in. It's located in county hall building, next to the main ticket office area, next to the eye itself. It runs continuously you just wait outside to go in. It only lasts about ten mins but is a great fun little attraction, even blows foam and air at you, clever lighting effects, you fly over London and see the landmarks etc. You put 3D glasses on. Have been on many times and never been asked to show Eye ticket. My OH said it's probably like this as it acts as a good Advert for the eye itself anyway.