Meghan Markle will be allowed to use Princess Diana's nickname for the Queen

The nickname is a more informal version of 'Ma'am'

Meghan Markle and the Queen appeared to bond during their first public outing together to Cheshire - but the Duchess of Sussex is not on a nickname-basis with her royal grandmother-in-law just yet.

Markle, who officially became a member of the royal family on May 19, currently refers to the 92-year-old monarch as ‘Your Majesty.’

But once the Duchess’s relationship with Queen Elizabeth II progresses past formalities, Meghan may choose call the Queen’s by something (slightly) less formal instead.

According to Ingrid Seward, editor-in-chief of Majesty magazine, after Your Majesty: “it is Ma’am, thrown into conversation as many times as possible.”

Meghan won't be the first royal to use the term of endearment - the term for the Queen was, apparently, a favourite of Diana’s, Harry’s late mother.

But if that still sounds a little formal, it may eventually be shortened further: “This can be shortened to Mama, when Meghan gets to know her as Diana did. But never her pet name Lilibet, which is reserved for very close family and friends,” Seward told Grazia.

Considering the progress of the pair’s relationship, it likely won’t be long before Meghan feels comfortable using the moniker.

Meghan and the Queen went on their first public engagement together (Getty)

Meghan’s invitation to join the Queen on the royal engagement to Cheshire aboard the royal train was an important opportunity for the Duchess, as it is a sign of the Queen’s confidence in her.

The pair bonded as they sat next to each other (Getty)

Comparatively, it was 10 months after the Duchess of Cambridge's wedding before she was invited on a similar outing with the monarch.

And judging by the smiles both royals wore during the opening of the new Mersey Gateway Bridge, Meghan will be calling the Queen “Mama” in the near future.