Royal couple Prince William and Kate Middleton haven't tied the knot yet - but already they are being torn apart.

New stamps designed by New Zealand Post that go on sale this week have a perforated line between the engaged couple, meaning they can be split up. Together the Niue Royal Wedding stamps are worth $5.80, but separated Middleton is a $2.40 stamp and Prince William a costlier $3.40.

The stamps go on sale on Wednesday and the concept has been described as "unusual" and "strange".

Monarchy of New Zealand president Simon O'Connor said the stamps were "slightly strange" and had not been designed well.

"It seems unusual and not well thought out, but it's not insulting. The monarchy has thick skin and they would even have a sense of humour about it," O'Connor said.

The president of the New Zealand Stamp Collectors club, Steven McLachlan, said the designers probably hadn't thought about what the perforated line could symbolise.

"Perhaps it's bad karma. I think they haven't thought it through properly," McLachlan said. Despite the poor design, he said, the stamps would be in demand by collectors.

"People from all around the world will buy this stamp in big quantities and they will love it."

According to Kapiti philatelist Ian Burtt, all stamps that displayed the royal family had to be approved by Buckingham Palace. "I believe Commonwealth stamps are not always approved and they are sent back with helpful hints as to what will make them more acceptable," Burtt said.

Meanwhile, when Prince William stayed a night in the small South Island town of Hokitika this week, he didn't demand royal treatment.

In fact, he washed down his whitebait fritters with lemonade at the four-star Beach Front Hotel.

Ocean View Restaurant and Wine Bar food and beverage manager Leanne Holland said the Prince dined with Prime Minister John Key and ate from the standard a la carte menu. Their entourage booked 26 rooms at the hotel on Thursday night after a visit to the Pike River families in Greymouth.

"He tried the West Coast whitebait for dinner and thoroughly enjoyed it. He didn't have any alcohol, he just had lemonade," Holland said.

She described him as a "charming gentleman" with great manners.

"I was really nervous, thinking he's going to be complicated, but he was a lovely, charming gentleman."

The Prince, second in line to the throne, stayed on the hotel's top floor in a room overlooking the Tasman Sea.

The room, which costs about $185 a night, had a king-sized bed, spa bath, a flat screen television and doors to the balcony.

William flew out of Wellington on a Royal Australian Air Force aircraft yesterday to meet victims of cyclones in Townsville.