It's the statue of Arthur Lowe as Captain Mainwaring in Thetford, Norfolk.

Most episodes of "Dad's Army" were filmed in the Breckland area of Norfolk nearby, and the cast used to stay in the town during the periods when series were filmed.

Larger size. And Mainwaring from further away with a nod to the Dad's Army title sequence. Pictures are from a visit to Thetford in November 2022.



Finn also met Mainwaring giving one of his interminable lectures.
"Now pay attention Finn!"


"Don't panic! Don't panic!"


As eightondee mentioned, a lot of location scenes were filmed in Norfolk. Some around the town of Thetford, where today there is a Dad's Army museum. The pictures above are from said museum. The second one depicts a scene from the episode Something Nasty in the Vault.

I visited the street in Thetford where a scene from probably the most famous episode, The Deadly Attachment ("Don't tell him Pike!"), was filmed.