Which English county has the shortest perimeter, Rutland or Isle of Wight?

Bit of a tricky one this because neither is really classed as a County. They are Unitary Authorities. However, of the two, the Isle of Wight has the smaller area, by 2 square Km, so should have the shorter boundary. Traditionally, before the Isle of Wight became an independent authority, as opposed to being part of Hampshire, Rutland was always the smallest county in England, apart from the few years when it was part of Leicestershire.

https://en.wikipedia.org/wiki/List_of_English_counties_by_area

A Unitary Authority is defined here:
Unitary authority - Wikipedia, the free encyclopedia

If you watched the tv show QI their researchers found that the answer to this question depended on whether or not it was high or low tide at the Isle of Wight