A further transatlantic cultural difference is that in the UK people are notably discreet about how they go about tipping and will make some effort to do so without it coming to the attention of the rest of their party, whereas in the US the opposite is true.

I have often thought that a useful addition to the inventory of a US waiter or valet parker would be a bullhorn, so those who have tipped more than the "going rate" (which itself seems to increase each year by well above inflation) could announce excitedly and at the tops of their voices to all the other patrons the amount of their largesse. Of course, a further $5 tip would be expected for the use of the bullhorn.