This classic K1 design of a telephone kiosk by Sir Giles Gilbert Scott in 1921 stands at the junction of Sherborne Street and the High Street Bembridge. There are other examples in museums, and indoors, but this is the only one still working out in the street where it started. So it’s fair to call it the oldest working street phone box in the country.
Yes, it does still work, and you can ring it up if you don’t want to put 60p in to try it out.
The GPO used the designation K for Kiosk to describe their public telephone booths. In 1921 the first Kiosk K1 was introduced. It was made of concrete panels with a wooden door and in the Mk234 version, wooden window frames. These were changed to metal in the Mk235. In 1927 the design was modified again to make it more like the newly-introduced K2 (the famous red telephone box which went on to become very widely used). This meant deeper window framing and revised roof signage. It became the K1 Mk236, which is the type that now stands in Bembridge.
This one is a Grade II listed building owned by Bembridge Parish Council, and the equipment inside belongs to BT.