The iconic 'SNL' alum and movie star strolled through the capital of England completely unnoticed Tuesday ... alongside his wife, Kelly Tisdale.

MM appeared to be checking out upscale spots in St. James, including Fortnum & Mason -- known for gourmet groceries -- and Selfridges -- a fancy department store.

The couple also stopped by The Armoury of St. James's -- a favorite for collectors and history buffs -- where Mike celebrated a purchase with a triumphant fist pump.

The visit was a far cry from what it would have been like for his Hollywood alter ego, Austin Powers, being chased through the streets of London by adoring fans ... mostly ladies, baby.

Mike has hinted the 'Austin Powers' story is far from over -- he is interested in a fourth film ... if the shagadelic stars align.

And, who knows? Maybe this trip to London was exactly what MM needed to get his creative mojo going for one more romp.