"Mandii was present at the reception, together with her nearly completed painting of Clarence House, and asked Camilla to add some finishing touches. She painted in a couple of ground floor windows and said they were her dining room windows."
Seven months later Ms McLachlan and the painting were again in the same room - this time at an auction in aid of the charity WW100, a fundraiser for New Zealand's World War I commemorations.
"I was particularly drawn to the painting because it was large and round and rather quirky and fun," she said.
After an "animated" auction, Ms McLachlan was successful and paid 1450 ($2921) for the painting.
"I am, in no way, an art expert - I just know what I like when I see it."
Ms McLachlan was brought up on a farm near Wanganui and attended Wanganui Girls' College. She left in 1977 to "see the world" and settled in London.