Transcription reads:

The Roman and Medieval City Wall
On this site stands a surviving piece of the Roman city wall.
The landward wall was constructed between A.D. 170 - 220
and extended a distance of 3km (2 miles). It was one of the
most costly works undertaken in Londinium.
The Roman city wall was 2.7m (9 ft) thick at the base and
stood over 6m (20ft) in height. This large defensive
Boundary imposed an important influence on the city’s
development. It continued to be of importance through the post-Roman and medieval periods when
It was extended and increased in height.

Followed by diagrams and statistics.