And before that, Kate lived in Lady Thatcher's elegant four-storey home in Belgravia.
As a trained private nurse, she worked fulltime for the former prime minister and served as her cook, her dresser and, most importantly, devoted friend and companion. Kate spent Christmases with the Iron Lady, cooking the turkey before they sat down to watch the Queen's broadcast.
And she accompanied her on rare outings to the park, ready to catch her in case she stumbled.
Kate was identified as a New Zealander in the Guardian this week in an article about Lady Thatcher's last days.
It said that among the last things she saw in the final hours before her death on Monday was a video of eight biscuit-coloured Dachshund puppies and their mother.
The former British Prime Minister died this week at the age of 87 after suffering a stroke. She was loved and loathed in the UK.
Lady Thatcher had become increasingly frail in recent years following a series of small strokes in 2001 and 2002.
Her daughter Carol also revealed in 2008 that she had been diagnosed with dementia, which had increasingly affected her memory for the past decade.