Royal sources told the outlet that the 36-year-old has been dedicated to the princess with the two women being “inseparable” in recent months.

Ms Archer, who has previously been pictured close to Kate while carrying her bags, is also said to have assisted her to and from hospital appointments.

The sources said: “Natasha deserves this boost – she’s unfailingly discreet and loyal to Kate. The salary boost will be welcome too. This appointment means we can expect to see Natasha by Kate’s side for years to come.

“It seems to be Kate’s way of thanking her for her loyalty.”

Ms Archer, who is married to photographer Chris Jackson, has also previously worked for the private office of the Duke and Duchess of Gloucester from 2007 until 2010.

She attended £48,000-a-year Uppingham School in Rutland and took A Levels in English, Art, Spanish and Italian.

She also studied Hispanic studies at King’s College London in 2005.