I bet because you were on the tube you didn't ask him why he was wearing the cap
( if you spontaneously start a conversation with a stranger on the London underground a tear would appear within the universe and before you could bling the whole of creation as we know it would be sucked in, never to be seen again !!! )
nope. but in our dialect of English here in the US known as General American, we refer to the television as the tube, and in the British dialect of English known as Received Pronunciation the tube is the subway.