The first glimpse of the coronation invitation shows the official use of "Queen Camilla", marking the transition from the title of "Queen Consort".

The ornately illustrated invitation, sent to about 2,000 guests, is from "King Charles III and Queen Camilla".

Her grandchildren will be among the pages at Westminster Abbey, alongside the King's grandson, Prince George.

With a month to go before the coronation, a new official photo of the royal couple has also been released.

The invite for the 6 May coronation, printed on recycled paper, shows the coronation will mark a change in how Camilla is titled.

A royal source suggested that in the initial part of the new reign it made sense to use "Queen Consort" as a way of distinguishing her from the late Queen Elizabeth. But from the coronation it would be an "appropriate time" to officially change to "Queen Camilla".

At the coronation service next month, Camilla will be crowned alongside the King, 18 years after the couple married.

And it is not much more than a year since the late Queen Elizabeth had addressed what was still the unresolved question of Camilla's future title.

The late Queen had given a public endorsement for Camilla, saying she should be called Queen Consort, at a time when there were still suggestions that she would be known as a Princess Consort.

Reflecting the King's many years of environmental campaigning, the artwork for the coronation invitation uses the folklore figure of the "green man", with features made from ivy, hawthorn and oak leaves.

According to Buckingham Palace it is a symbol of spring and rebirth which celebrates a new reign.

The design by illustrator Andrew Jamieson also includes images of the natural world, including wildflowers, birds and insects, as well as national and heraldic emblems.

But with the coronation approaching, it is still not clear whether the invitation for Prince Harry and Meghan, Duchess of Sussex, is going to be accepted.

A spokesperson for the California-based couple said this week there was no update on whether they were attending.

Last week the King completed his first state visit, receiving a warm welcome in Germany. But the focus is now on preparations for the coronation.

Roles have been given to children of friends and relations, with eight "pages of honour" announced to take part in the ceremony.

This includes Prince George, the nine-year-old son of the Prince and Princess of Wales, and three of the Queen Consort's grandchildren, Gus and Louis Lopes, Freddy Parker Bowles and her great-nephew Arthur Elliot.

The new official photograph of the King and Queen Consort was taken last month in the Blue Drawing Room in Buckingham Palace.

It follows an announcement by the Cabinet Office of another photo of the King, with public places such as council offices, courts, police stations and schools being invited to apply for a framed photograph of King Charles.

But anti-monarchy campaigners criticised the £8m budget for the new pictures, saying that it was a waste of public money at a time of funding pressures.

The Cabinet Office would not give a breakdown of the contract for the framed photos, but said details would be "announced in due course".

It is also understood that there will be no overall figure for government spending on the coronation until after the event.