The official anthem of England, being a country within the United Kingdom, is that of the United Kingdom, namely "God Save the Queen". All the countries of the United Kingdom, however, have unofficial local anthems of variying degrees of popularity and official-ness; England's anthem in this regard is harder to determine.
The way national anthems of the countries of the United Kingdom are often determined is by what is played at sporting events, especially those where play against other British countries are concerned. In some, "God Save the Queen" is used for England, even in play against other areas of the United Kingdom where their respective local anthems are used, in a few others another patriotic somg might be used (the most popular of which is "Jerusalem"), but the one most often used for England, such as important events like the Commonwealth Games, as well as in national anthems publications and musical compilations (as an area separate from the United Kingdom, of course), is "Land of Hope and Glory".
Taken from Edward Elgar's "Pomp and Circumstance March No. 1 in D", this patriotic song may be familiar to N. American audiences as being played at convocation ceremonies. The song was first performed in 1901 and, at the request of the new king of the United Kingdom, King Edward VII, words were written for the occassion of his coronation the following year. The words were written by Arthur C. Benson.
One must keep in mind that no anthem has been decreed by law as the official national anthem of England (even "God Save the Queen" is used traditionally as the national anthem of the United Kingdom, having not beed officially declared as such.); and "God Save the Queen" seems to remain the most popular anthem within England.
The stamp above features Sea Pictures, a composition by Edward Elgar, the anthem composer, issued in 1985.