However, a Palace source, speaking to the BBC, disputed reports that Prince Harry and Meghan had spoken to the Queen before the birth about using the name.
According to the Mail’s Royal editor Rebecca English, this remark set off a firestorm and showed the Royal Family “standing up” to the couple in California.
A spokesman for the Sussexes’ insisted they would not have used the name had the Queen not been supportive.
Ms English claimed on the MailOnline’s Palace Confidential the disagreement among Palace sources with the initial claim against Harry and Meghan shows the Royal Family pushing back.
The royal expert said: “Absolutely, it is really significant.
“The BBC’s report produced an absolutely stinging response from the Sussexes.
“First through a spokesman saying the Queen was the first person they called and that they would not have gone ahead with the name if the Queen was not supportive.
The Lilibet nickname was first coined when then-Princess Elizabeth was couldn’t pronounce her own name properly as a toddler.
The Queen’s late husband, the Duke of Edinburgh, also called her by the nickname.
In other news, the Duchess of Cambridge has said she “can’t wait” to meet her new niece.
Kate said she wished the Duke and Duchess of Sussex’s newborn daughter “all the very best” when asked at a G7 summit of world leaders in Cornwall.