I work for the Proudman Oceanographic Lab ex Bidston now based in Liverpool.
The experiment would have been done using one of our Absolute Gravimeters which (very) accurately measure the gravity and therefore tiltyness (scientific ehh!)
I will email the guy involved if you like, what do you want to know,
Cheers
Steve
May the fleas of a thousand camels infest the crotch of the person who
screws up your day and may their arms be too short to scratch.