I would love to buy some, but I don't really think I can justify £20 plus per tee shirt. More importantly, just how wierd is that.
Archigram are fairly well known, if you are interested in that sort of thing, they developed theoretical projects such as a walking city, or a plug-in city, somewhat obviously these were never built, but they did serve to inspire the profession.
But why on earth would the japanese select archigram out of all possible sources for a range of teeshirts. There is a sort of manic futurism about the japanese, that chimes well with the work of Archigram. Perhaps the quiet considered British are just going to get left behind.
