They were the two most powerful women in the country and they were forced together by circumstance.
Margaret Thatcher was the Queen's Prime Minister between 1979 and 1990.
And as PM she was one of the lucky few commoners to be granted an invite to the Queen's favourite castle, Balmoral.
Her Majesty spends time at her estate in Scotland every summer.
It's a much-needed break for the dedicated monarch, who is often joined by several members of the royal family.
The Queen also extends an invitation to the serving PM.
Highlights of the summer trip include walking in the Highlands, picnics, fishing, grouse hunting and the famous royal BBQ.
This is a royal meal unlike any other, as those who work in the royal kitchens have revealed.
Channel 5 documentary Secrets of the Royal Kitchen explains what the royal family really eat and how they like their food prepared.
And despite having a huge staff and their disposal, ready to cook the finest foods, there is nothing the royals enjoy more than their annual outdoor feast.
It's where they get to relax and let their hair down - and like any BBQ, most of the fun is in the cooking.
The Queen and Prince Philip are involved in every stage of planning the meaty feast.
Former royal chef Des Sweeny said: "Prince Philip helps to chose the ingredients for the BBQ and the Queen makes the salad."
The Duke of Edinburgh has been snapped grilling sausages and cooking huge lumps of meat on the royal BBQ.
There's another key difference to this meal compared to all the others eaten by the royal family - they serve themselves.
Royal biographer Lady Colin Campbell said: "It's all served on fine china and nice silver but they do serve themselves."
And what happens to the dirty dishes when this outdoor feast is over?
Darren explained: "Afterwards, the Queen would rinse and scrap the dishes - imagine that."
Margaret Thatcher reportedly refused to ditch her high heels, even for a trip to Balmoral and was said to have once been forced to borrow a pair of wellies from the royal family so she could go on a walk around the Scottish estate.
One year, when she was Prime Minister, Thatcher's visit coincided with the royal BBQ - and she was stunned that the Queen did her own washing up.
After she returned home she sent Her Majesty a very unusual gift.
Lady Campbell explained: "Once, when Mrs Thatcher was up at Balmoral, she noticed that the Queen was doing the washing up without gloves.
"So Mrs Thatcher went and bought her some rubber gloves and sent them to her, which is rather sweet."
The programme also reveals the Queen enjoys nothing more than eating her evening meal off a tray in her living room in front of the television.
Each year the royal family spends £1.6million on food and entertains 50,000 people.
- Secrets of the Royal Kitchens is on Channel 5 at 9pm tonight.
