Attention Earthlings: The Martians are already here!

Early Sci-Fi series with a dour, matter-of-fact documentary feel to it. In realm of science fantasy TV, Prof Quartermass was a precursor of the more famous Doctor Who. Archaeological dig in Knightsbridge (Harrod's basement extension?) has a bunch of British military types fossicking around in the clay & dirt, they find evidence of ancient & hostile alien life form. With the fullness of hindsight, the archaeologists would have been wiser to dig in China instead, as unearthing terracotta warriors is much safer than unearthing Martians!