To the delight of locals, the stars were also spotted wandering around Oamaru's Victorian Precinct on Saturday.
An Oamaru resident and Harry Potter fan Matthew Wicks stopped and spoke to the pair in Harbour St.
"They said they had been around the historic precinct and [said] how beautiful it was,'' Mr Wicks said.
"[They] didn't say exactly where they had been, just said they loved the old part of town.''
After his encounter with the British actors, Mr Wicks said he spoke to others who had their photo taken with the pair and everyone had commented that they "were very nice about it''.
It is understood they stayed two nights at Pen-y-bryn Lodge, but the owner of the Oamaru luxury lodge, James Glucksman, declined to comment.