He has been included in an internal email accidentally. Unprofessionally. His data has been mishandled. And fortunately he got it but evidently anyone else could have been mistyped or mistook onto it.
Its a Data Protection Fault. And how else can you tell? They called him!!! Because they know! It is a Data breach. Also may I add his internal email has been sent externally fortunately to him. But still a data breach. Also it contains the internal comments on it. So yep have a very boring read on Data Protection in the civil service it is very comprehensive.
I see someone else called you out on it. The council phoned him up because they were likely embarrassed about their reply.
"but evidently anyone else could have been mistyped or mistook onto it." - yes good luck getting that to stand up in court.