Probably 19th. January 1952 at the 5 Nations Rugby Union match at Twickenham (England vs Wales). I would think that it wouldn't have been played at either the following France vs Ireland match on 26th. January or the Wales vs Scotland match on 2nd. February. England didn't play again until 15th. March, although other 5 Nation matches were played, the long gap probably due to a period of mourning/respect.
England's first international football match wasn't until April 1952, after the King's death.