Roman Wall?

This is a section of wall outside the Parrot public house.

"The Roman wall was ... more than five feet thick as can be seen in front of the Parrot restaurant in St Radigan's." (Birmingham 2015, 43)

I can't see any evidence that this is a Roman wall but I don't really know what I am looking for, except for thin red bricks as can clearly be seen in the picture of St Martin's church on this page. 

The Parrot's website tells us that it is "One of Canterbury’s oldest buildings, ... built on Roman foundations in the 14th century"

There is a plaque next to this wall which says that this is the Roman wall but it was made higher and incorporated into the wall of St Mary's church. That's this wall:

You can see traces of red brick in the lower sections of the wall although they are fatter than what I would typically expect to see. Any Roman brick experts out there?