Well, two things may be going on. The sea may be rising or the land may be sinking—you’d see the same result in either happening. However there is a “path” in Britain, called the Broomway that is flooded every high tide that people have been using for at least the last 600 years, so if the sea level is rising, the land in Essex is coincidently rising at exactly the same rate.
Informative: thank you!