Balmoral's daily schedule includes five outfit changes per day

Queen Elizabeth is currently enjoying her summer holiday at Balmoral Castle, in the Scottish Highlands.

But it's not all relaxation at the sprawling estate, where the daily schedule can be rather involved – including having to change outfits up to five times a day.

Each year, the monarch is joined by members of her family who come to stay with he and Prince Philip, anytime from August until October.

Most recently, the Duke and Duchess of Cambridge – and their three children Prince George, Princess Charlotte and Prince Louis – stayed at Balmoral over the public holiday weekend.

The Duke and Duchess of Sussex, and baby Archie, are expected to arrive any day now for their turn.

Prince Charles and Camilla, the Duchess of Cornwall, are staying at Birkhall, the late Queen Mother's house within the Balmoral estate.

Prince Andrew and Sarah Ferguson, and their daughters Princess Beatrice and Eugenie, and the Earl and Countess of Wessex, and their two children, have also spent time with Her Majesty over the past month.

"It can get quite busy at what they call 'the big house' and it's not especially relaxing even though it's a holiday," a source told Vanity Fair.

"There's a daily routine which evolves around meal times, several outfit changes every day, sometimes five, and the Queen likes everything to run like clockwork."

Balmoral's daily schedule is informal and outdoorsy. Regardless of the weather, picnics, barbeques, brisk walks, fishing and horse riding are all vigorously encouraged. 

Her Majesty swaps her usual brightly-coloured outfits – typically worn during royal engagements – for country tweed, greens and browns. She's often pictured behind the wheel of her Land Rover, wearing a headscarf, warm tartan and boots.

But each week, Her Majesty attends church at nearby Crathie Kirk where she is dressed in her Sunday best.

"It's the one time when the Queen is mostly off duty," royal historian Hugo Vickers said.

"Although her work goes on and the red boxes keep coming, along with the PM and other guests, it is a more gentle pace for her and her time is largely her own."

British Prime Minister Boris Johnson and his girlfriend, Carrie Symonds, are due to travel to Aberdeenshire to stay with Her Majesty shortly, as per tradition.

It's understood Ms Symonds, 31, will be the first unmarried partner of a sitting PM to stay at Balmoral.