Wiktionary
the british are coming
phr. 1 A warning that enemies are about and a battle is about to begin. 2 A statement of impending doom.
Wikipedia
The British Are Coming (song)
"The British Are Coming" is a song by the American rock band Weezer from their ninth studio album Everything Will Be Alright in the End. While the song has not been released as a single, it was the third song from the album to be publicly available on stream prior to release, after " Back to the Shack" and " Cleopatra", and was made available to download with album pre-orders.