New Zealand Post has had to recall its Royal Wedding presentation packs, after a mistake was made.

The packs say William was born on May 21, while his actual birthday is June 21.

Ivor Masters, their Head of Philately, said: 'We do have external writers and our own internal checking system, but for some unfortunate reasons, this mistake has happened.'

The packs will be reprinted and available next week.

This video, from TVNZ, shows the woman who discovered the mistake, Ivor Masters and stamp dealer Len Jury. (It also contains a word not suitable for broadcast on pre-watershed British television).