Well I wondered about Wayland's Smithy, which was restored in the 1960s, see the 'before' photo @ http://www.themodernantiquarian.com/post/146363/waylands_smithy.html
and how it looks today, James Dyer said "There seems to have been a rather more formalised 'restoration' in which the flanks of the barrow were sharply revetted to form walls. "
It looks good today, a truly 'romantic' interpretation of a long barrow but it has been visually altered by later hands, but then as it had two phases in its construction should we complain or allow history to add other layers of interpretation?