He'd love the chance to get close to the Prince, perhaps shake his hand, and has been thinking about what to say if he gets a chance.
"I wouldn't push my way up to the front, but if I was close enough I would certainly say something. I would say to him, 'I hope you are enjoying your stay, and welcome'.
"If I had 30 seconds of time I would tell him it was an honour back in 1983."
Mr Terewi is planning to wear all his medals for the occasion. They are for active service on the Thai border, in Malaya, in Borneo, in Vietnam and in Antarctica. He'll also be wearing his 1980s-issue peak cap, and carrying the pace stick he received when he became a regimental sergeant major (RSM) in 1980. He's been able to keep the stick because his 1st Transport Regiment was later disbanded.
As a RSM he was one of 14 soldiers acting as quarter guards for Charles and Diana when they visited New Zealand in 1983.
The 14 soldiers were stationed at the gateway to Government House.
They took two-hour shifts to patrol the area, day and night, and their main duty was to present arms when the royal party left and returned from functions.
After the royal party left, everyone involved in the visit was invited to a garden party at Government House.
At the party one of the aides told Mr Terewi the Governor-General - Sir David Beattie at that time - wanted to see him, to pass on a message from Prince Charles.
"He said, 'I have a message for you from His Royal Highness. He said you look like Idi Amin'."
Mr Terewi thought the peak cap he wore might have helped his resemblance to the feared African leader.
"I thought that was quite funny," he said.
