Methinks that the opening and transitional trumpet piece in the famous All you need is love by The Beatles is clearly borrowed from the identical trumpet piece in the sparkling and rousing Overture 1812 by Tchaikovsky. The recognition of the resemblance is not very pronounced, but quite clear when you listen to the two pieces a couple of times.
Or maybe this is simply a 'well-known' fact that has escaped my attention. Any corroborations?
Recall that Overture 1812 was used to spectacular effect in V for Vendetta