Well, notwithstanding the last post, the Oxford English Dictionary uses capitals for French, German, English and so on, whether these be adjectives or nouns.[see Eng Teach's link for an explanation]. The only exception is 'english' , in American English, meaning 'side', as in spin imparted to a ball in billiards or pool: 'He hit the ball with english'.This is given in the OED as' English (also english)', so that may be with or without capital E.
Rather more confusing is 'north'. In general we write 'north' for both adjective and noun.However, we frequently write 'North' instead when referring to the northern part of a region, country, area etc or the people of it.That's a separate practice from following the rule that a proper noun which includes 'north' is written with a capital e.g. the North Pole.The same practice and the same rule also apply to 'south', 'east' and 'west' .