King Charles has delivered a personal video message remembering the life of public service of his "darling Mama", the late Queen Elizabeth II, on what would have been her 100th birthday.

The King warned, in a message recorded at Balmoral earlier this month, that his mother would have disapproved of the current state of the world.

"Much about the times we now live in, I suspect, may have troubled her deeply," said the King, without revealing any specific concerns, domestic or international.

On Tuesday, which marks the centenary of Britain's longest-reigning monarch, the final design of a traditional bronze statue of the late Queen will be shown to King Charles and Queen Camilla.

The statue, to be sculpted by Martin Jennings, shows the late Queen in her younger years, in the ceremonial robes of the Order of Garter.

The image, which will be 9.84ft (3m) tall, standing on a 11.15ft (3.4m) plinth in St James's Park, is inspired by the 1955 painting of the late Queen by Pietro Annigoni.

It's being unveiled 100 years after her birth, on 21 April 1926, when the then Princess Elizabeth was born in a townhouse in Bruton Street in Mayfair.

Lord Janvrin, chairman of the Queen Elizabeth Memorial Committee, said the image showed her in her public role; if the statue had shown her on horseback, as had been discussed, it would have been more about her personal hobby.

The memorial committee had to decide how to represent the late Queen to future generations and Lord Janvrin said they had wanted to show her "very strong sense of duty" and sense of public service.

In his video message, the King said the late Queen lived through "remarkable change and yet, through each passing decade, through every transformation, she remained constant, steadfast and wholly devoted to the people she served".

The memorial project in St James's Park, designed by a team headed by architect Lord Foster, also includes a bust of the Queen in later years and a bronze statue of Prince Philip.

A bridge across the park will be rebuilt, with a glass balustrade that will evoke a royal tiara.

It's expected that these memorials, in the central London park near to Buckingham Palace, will be completed in about two years.

As well as the statues in London, there will be a digital section of the memorial project, with a website that will invite people to send in their own memories of the late Queen.

The website Queenelizabeth.com had belonged to the shipping company, Cunard, but has now been donated to the Queen Elizabeth II memorial.

It will build a historical archive of memories, a social history of royal events, and will be supplemented by a digitised version of the "court circular", which records the working lives of the Royal Family.

There will also be a nationwide memorial scheme, in which a newly created Queen Elizabeth Trust will support local community projects, intended to bring people together.

The King, who will be going on a state visit to meet US President Donald Trump next week, spoke of the late Queen's legacy of optimism that "goodness will always prevail and that a brighter dawn is never far from the horizon".

The King called for a "happier tomorrow" to be "rooted in peace, justice, prosperity and security".

He also recalled how many might remember the late Queen from "a fleeting personal encounter, a smile, a kind word that lifted spirits … or for that marvellous twinkle of the eye when sharing a marmalade sandwich with Paddington Bear in the final months of her life".