TBF the team can trace their roots back to Wasps FC.
I don't really have an issue with the pro team but they been migrationary unlike other clubs in premiership and moving from London into the middle of the midland heartlands stings a fair bit. Saracens have pretty much always been NW London and Quins have been playing in Twickenham since the early 1900's. London Irish do play in Reading though.
However other teams that recent celebrated 150 years are Bath (who've always played in Bath) and Sale (who have moved but barely). Quins as noted have moved but not for an extremely long time.