"Flowers of the Forest"
From Tardis Wiki, the free Doctor Who reference
"Flowers of the Forest" was a song that Angus MacRanald was playing on his bagpipes upstairs in the Fox Inn while the Fourth Doctor was downstairs. When Sarah Jane Smith complains about the noise, the Doctor- in an uncharacteristically somber tone- comments that it's a "lament for the dead". (TV: Terror of the Zygons)
