The Barnet Bypass was a street in the London Borough of Barnet. A police box, which was the last of its kind left in England, was located in a lay-by there.
History
On 28 February 1981, the Tremas Master materialized his TARDIS around the police box and killed a policeman who was using the telephone. Later, when Tegan Jovanka's Aunt Vanessa's car broke down, Tegan went looking for help and entered the Doctor's TARDIS, thinking it was a real police box. (TV: Logopolis [+]Christopher H. Bidmead, Doctor Who season 18 (BBC1, 1981).)
When Tegan, who was suspicious of Vislor Turlough at the time, stated that humans don't just walk into transmat capsules, Nyssa reminded her that she did just that with the TARDIS on the Barnet Bypass. (TV: Mawdryn Undead [+]Peter Grimwade, Doctor Who season 20 (BBC1, 1983).)
When Prince Genei came to Earth to conquer it, he landed his craft near the Barnet Bypass, where he mistook the police box for the Doctor's TARDIS and departed. Shortly afterwards, workmen arrived to take the box away. (PROSE: Useless Things [+]David Carroll, Brief Encounter (1994).)