We can see from Terry that accent is potentially influenced by social class.
We can also see that how strong your accent is fluctuates due to social situation. Terry might not necessarily demonstrate this exactly point, but it's a general observation we all make.
It often fluctuates between Reserved Proununciation and, for example,
Bristolian. The people you'd often see using Reserved Proununciation, are teachers/doctors/bankers and headteachers and you'd use it in job interviews.
But people that would use the Bristolian accent would be random, casual people on the street, or friends. And you would use this type of accent is used in casual/social situations. And example of this, is Terry.
The ability to fluctuate between Reserved Proununciation and Bristolian is called "Bi-Dialectism".