Second the London Eye. It gets some flak for being an over priced tourist attraction, but the views can't be beat (weather conditions permitting of course). It is a tad bit expensive, but I doubt he's seen or been on something like that before (I think it is the second or third largest ferris wheel in the world). When I went years ago, there was a discount if you kept your BA stub, as it was sponsored by BA at the time. Not sure if that's still the case.