Coiffed and cradling their newborns dressed all in white, it is a remarkable portrait of motherhood in the Royal family — unseen since it was captured 60 years ago.

The image, taken by Lord Snowdon, shows Queen Elizabeth II, Princess Margaret, Princess Alexandra and the Duchess of Kent holding their newborn babies in 1964.

Lord Snowdon, Princess Margaret’s celebrated photographer husband, took the picture as a token of thanks for Sir John Peel, the royal obstetrician who delivered all four babies within two months.

And it has lain hidden in the Royal Collection until today — when it goes on display in a new exhibition, Royal Portraits: A Century of Photography, at The King’s Gallery in Buckingham Palace.

On the far left of the photograph is the now 87-year-old Princess Alexandra, the Honorable Lady Ogilvy and first cousin of the late Queen Elizabeth. She holds her baby son James Ogilvy, born on February 29, 1964, who is now a landscape designer.

He was followed by Prince Edward, born to the Queen a month later at Buckingham Palace.

On May 1, Princess Margaret, who sits on a cushion on the floor, gave birth to Lady Sarah Chatto, who continues to work as an artist. on the right is Katharine, duchess of Kent, now 91, holding Lady Helen Windsor, who went on to work in fashion.

The charming picture will be displayed along with a handwritten letter from Princess Margaret to her sister, asking her “darling Lilibet” to sign a print “as a souvenir of an extraordinary two months of delivery”.

She also offers her “a hundred million thanks” for having them all for the photo shoot.

The exhibition — the first at The King’s Gallery since it was renamed following the death of Queen Elizabeth — charts the evolution of royal portrait photography from the 1920s to the present day.

It includes the Queen Mother’s personal copy of her daughter’s Coronation portrait and the earliest surviving colour photographic print of a member of the Royal family, taken in 1935.

The majority of the more than 150 photos from the Royal Collection and Royal Archives are being displayed for the first time.

Curator Alessandro Nasini said: “The Royal Collection holds some of the most enduring photographs ever taken of the Royal family, captured by the most celebrated portrait photographers of the past 100 years — from dorothy Wilding and Cecil Beaton to Annie Leibovitz, david Bailey and Rankin.”

Unreleased wartime images by Cecil Beaton include one picture of King George Vi and the Queen Mother inspecting bomb damage at Buckingham Palace in 1940. The exhibition runs until October 6.