Australia's 25th prime minister John Howard met Her Majesty the Queen 25 times.

He reflects on his time with her and what she has done for Australia and stability in the western world in an interview with Liam Bartlett on 6PR Mornings.

"Right up until the end, the footage of her receiving Liz Truss ... apart from the Holy See in the Vatican, the British Monarchy is probably the oldest institution in western civilisation," Howard said.

"She is a person who had a terrific sense of humour, a person who was intimately curious."