To my knowledge the UK three squarish pin plug (or more correctly the socket which requirees this plug - this is a uniquely British design) is only in general use in countries which are or were within the Empire/Commonwealth, although they are to be found among the collection of options available in some countries such as Saudi Arabia where a wide variety is in use (i.e. no reliably consistent standard). Three pin plugs of other design are widely in use in order to include an earth connection, anything from the weatherproof round pin type seen In Britain as in Europe (e.g. on caravans, campers, etc.) to the French, US and Japanese three pins. As already stated by another respondent, the earth connection is sometimes accommodated (as on the Continent) on the side of the plug, not with a pin.