Blimey, I thought I knew a fair bit about Led Zep but there you go - they were accused of 'acquiring' quite a lot of their blues based stuff but hadn't heard of that one as well.
Most people think was a Led Zeppelin original but was actually first done by The Yardbirds back in the 1960's, mind you their version didn't last 30 plus minutes...
Pretentious and overblown or wonderful? Possibly all three.
https://www.youtube.com/watch?v=bCKqlVU99rk