They met on a blind date in 2016 after being set up by a mutual friend but it was months before the world knew they were an item.
At that time, Meghan was living in Toronto and still working on legal drama Suits, but had jetted to London several times to spend time with Harry.
And in October 2016, around Halloween, Harry is said to have visited Meghan in Canada.
It shows her posing in a chunky knit cardigan holding a huge carved pumpkin with a smiley face. Maybe the couple carved it together?
However, that Halloween was also the last one they enjoyed before their romance went public.
And it was at a Halloween costume party where they received a devastating phone call that left them worried.
As their relationship grew stronger, the couple started braving the outside world more and quickly discovered that people in Meghan’s Toronto neighbourhood weren’t that interested.
So when it came to Halloween, they both knew they wanted to go out and celebrate so came up with a plan.
In the unauthorised biography, Finding Freedom, royal reporters Omid Scobie and Carolyn Durand say the couple was having the “perfect” evening at Soho House – until a phone call ruined everything and changed Meghan’s life forever.
They write: “They especially didn’t feel like spending Halloween weekend in hiding, as there was much to celebrate.
“Some four months into their relationship, they were madly in love and eager to take part in the fun of one of their favourite holidays.
“The evening of October 29, with Harry in town, the couple decided to go to a big costume party being thrown at Soho House in Toronto.”
The couple bought Venetian-style masks which meant they could go about the party anonymously and nobody knew they were celebrating alongside a prince.
Harry’s cousin Princess Eugenie was also at the party with her now-husband Jack Brooksbank, and the two couples were having a great time until the prince got an unexpected phone call.
A newspaper had found out about their relationship and was going to go live with a story the following day.
The authors write: “A cocktail or so into the party, they were both feeling relaxed, absorbing the Halloween spirit.
“It was possibly the perfect night out – until they received a call from one of Harry’s aides at Kensington Palace. It wasn’t good news.”
They were reportedly upset and angry that their secret was out, understanding that the media and fans would quickly be fascinated by their lives, both separately and together.
Since that day though, they have married, welcomed two children, stepped down from the royal family and are now carving out a new life for themselves in California.