I just picked up Steeleye Span's latest offering "The Green Man Collection". I was listening to the title(?) track, and it starts (about 10 seconds in) with a guitar riff that I swear I have heard on another song (I'm fairly sure another Steeleye track). I can't place it for the life of me, however.
Although the song is dated to (circa) 1983, it's not been released before, so it's unlikely that I'm remembering hearing this track somewhere, and the rest of the track certainly doesn't ring any bells.

Anyone with a better memory than mine able to tell me where I've heard this before?

Here's the track "Green Man (1984)" on YT
The riff I mean plays at 0:10, repeated twice.