If I recall correctly it was called Exercise Powerhorn. A mixed contingent from across the Regular Force Army. The guidon of Queen Alexandras Regiment was carried.
They carried out ceremonial duties in London then were attached to various British Army units. Members of the Guards brigade travelled to NZ to teach the colonials how it was to be done and it had to be EXACTLY as they said. I wonder if we would accept that today.
All the tricks were played on then like the junior office commanding the Tower guard being slipped a live mouse rather than the keys he was expecting during the changing of guard ceremony.
Due to the reduced size of the Guards Brigade and their operation commitmentsI think it is shared with other UK services far more regularly. Heck they even ocassionally let the RAF (Regiment) loose doing London Public Duties.
The 'mouse' incident was at Buckingham Palace on the first change by the NZ unit. The officer involved was Major Frank Rennie, founder of the SAS and one of our great warriors. He was officer commanding the new guard and the officer in charge of the retiring guard was meant to do the pretend handover of the keys and added the mouse. Rennie to his credit did not flinch. The UK media made much of the Kiwi unit, and given that the duty was in mid winter marveled that the kiwis did not wear graet coats whilst the Guards did. Truth was that being NZ Army, the only great coats available were WW2 issue seconds and looked awful. It took about ten days for UK tailors to fix them for our troops. The Guards never mentioned this to anyone to try and save some dignity.