Zonal enforcement field

A Judoon platoon in search of a fugitive descended upon Gloucester and put a zonal enforcement field around the city, which prevented anyone from getting in or out. The Thirteenth Doctor matched the TARDIS rotation to the enforcement field's refresh rate in order to slip her and her companions in without anyone noticing. Jack Harkness attempted to make contact with the Doctor from a stolen spaceship, but failed to get accurate traces of her because it was a Level Seven Enforcement Field, which "interfered with everything". (TV: Fugitive of the Judoon)