Thank you, Yagan Kiely, it's way past time that due credit was given to George Martin, and not just for the Classical influences found in Beatles music.
Without him --- well who knows?

The Beatles are classical music. When visiting a few music CD shops worldwide, I saw them classified under "Classical". Admittedly, these shops had no (or very little) music older than the Beatles'.

Quotations of earlier music or use of earlier styles had always occurred and will always be occurring, because this is what music is about. Some musicians like to give sometimes a touch of "old" in order to sound interesting or to prove that they know their classics. That happens in any type of music.

Beatles classical?

King Crimson or The Doors are much more classical than beatles, they are just hippies

There are many people who are entirely unaware of any distinction between the terms "classic" and "Classical". The filing of Beatles records under "Classical" is a clear example. People watch Classic FM TV and expect Classical music; they will usually be disappointed.
Prog Rock may have generated some long and quite scintillating pieces - ones that spring to mind are "Supper's Ready" by Genesis, "Lizard" by King Crimson, "Echoes" by Pink Floyd, "Passion Play" by Jethro Tull, "The Gates Of Delirium" by Yes, and "Eruption" by Focus - but they are not organised in a Classical manner. Plus, many of us have heard pieces of flashy, pretentious, shallow, overblown widdling that sounds a bit like something by Bach, who didn't write Classical music. Very sad.
BUT there is one piece that I know of that comes close: King Crimson's "Starless" on the "Red" album. It loosely conforms to sonata form. Rather than straining for effect, it achieves an intensity, a kind of bleak majesty, that is exceptional in the rock idiom. It does this by means of a roughly Classical way of using its themes.

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"Music is a social act of communication among people, a gesture of friendship, the strongest there is."
- Malcolm Arnold.

The truth is that the English language (as French or Italian, to my knowledge) lack a proper term to describe accurately what most of us mean by "classical music".

In Polish (which I happen to speak as well), there is a great expression: muzyka powazna, which means "serious music". That's what we should be using in English, and it would avoid any misunderstandings.

Couldn't agree more, Kiwipolish. Over the last few years, particularly since the advent of Classic FM in the UK, the words classic and classical have been subjected to serious misuse and abuse.
I tend to use the word "serious" instead of classical, but just to play Devil's Advocate, it could be said that most "composers" of any age were perfectly serious when they put pen to paper, whatever the end result may have sounded like. The word is however, a more acceptable alternative.