King Charles's daily workout routine reportedly includes doing headstands in his boxers to help deal with back pain ailments after years of playing polo.

The royal's 12-minute regime, which was first revealed by his son Prince Harry in the memoir Spare, is said to start off with 'press ups, sit ups, the whole lot', according to Channel 5's Inside Windsor Castle - which is on at 9pm on Channel 5 this Saturday.

Presenter Xand Van Tulleken added however that his mother however had a less active morning set-up.

'The late queen preferred a gentler start to her day,' he said. 'A cuppa and a biccie or two were apparently enough for her.'

The Duke of Sussex, writing in his tell-all book, added that his father would perform the exercises daily - and that there was always a risk of accidentally walking in on the King - 'in just a pair of borers, propped against a door or hanging from a bar like a skilled acrobat' - in Balmoral if you accidentally opened the wrong door.

King Charles 's daily workout routine reportedly includes doing headstands in his boxers to help deal with back pain ailments after years of playing polo. Pictured with Camilla in February

The royal's 12-minute regime, which was first revealed by his son Prince Harry in the memoir Spare, is said to start off with 'press ups, sit ups, the whole lot', according to Channel 5 's Inside Windsor Castle - which is on at 9pm on Channel 5 this Saturday. Charles pictured aged 26, left, and aged 70, right

'If you set one little finger on the knob you'd hear him begging from the other side: No! No! Don't open! Please God don't open!' he penned.

However, it is not known if the routine is still part of the monarch's itinerary - or how long ago Harry would have stumbled into him working out. 

It comes as last week His Majesty got the go ahead by doctors to return to public-facing duties after being diagnosed with cancer.

Officials have stressed that His Majesty's treatment for cancer is still ongoing, saying: 'His Majesty's treatment programme will continue, but doctors are sufficiently pleased with the progress made so far that The King is now able to resume a number of public facing duties.

'Forthcoming engagements will be adapted where necessary to minimise any risks to His Majesty's continued recovery.'

They are not able, at this stage, to specify how long it will continue. A spokesman said: 'It is too early to say, but His Majesty's medical team are very encouraged by the progress made so far and remain positive about The King's continued recovery.'

They added that 'any public-facing engagements will be announced nearer the time in the usual way, and will remain subject to doctors' advice' and stressed that it would not be a 'full summer programme'. 

In February, his cancer battle was said to be changing his normally regimented daily routine, with doctors insisting he start work later, finish earlier and stop skipping lunch.

The monarch is also well-known for his strict eating habits, skipping lunch and eating a late dinner - a habit he has kept over many years. Pictured in 1974

The monarch has been told he will have to implement a number of new lifestyle changes to remain as healthy as possible, including cutting back on the time he sits at his desk.

Charles, who has been described as a 'workaholic' by his wife Queen Camilla, has long been admired for his strong work ethic, burning the midnight oil and working long into the night. 

But doctors' orders will mean the King would have been encouraged to work fewer hours, including pushing back his daily morning meeting with his private secretary, Sir Clive Alderton, from its usual 8:30am slot.

The monarch is also well-known for his strict eating habits, skipping lunch and eating a late dinner - a habit he has kept over many years. But the King will now be advised to eat regular meals instead.

His former press secretary Julian Payne told The Times: 'The King doesn't eat lunch; so, an early lesson I learnt when out on the road with him was to have a big breakfast or bring a few snack bars with you to keep you going.

The King also undertakes a rigorous daily exercise regime, which is inspired by the Canadian Royal Air Force, involving sit-ups and push-ups. Pictured in 1980

Aides also told the outlet that he 'wishes to continue' with the 5BX plan, an 11-minute workout. Charles earlier this week

'The working day is pretty relentless. Beginning with the radio news headlines and a breakfast of seasonal fruit salad and seeds with tea.

According to his friends and former staff, the King religiously takes a break at 1pm every day, not to eat, but to stretch his legs outside for a stroll and some fresh air.

The King also undertakes a rigorous daily exercise regime, which is inspired by the Canadian Royal Air Force, involving sit-ups and push-ups.

The 11-minute 5BX Plan 

1.  Bend forward and touch the floor, before stretching back up as if to touch the ceiling with your fingertips. Repeat this twice. (Duration: 2 mins)

2. Lay on your back and sit up far enough that you can see your heels. Repeat this three times. (Duration: 1 minute) 

3. Lay on the floor, raise your head and one leg. Repeat this four times. (Duration: 1 minute)

4. Lay on your front, straighten your arms and lift your body in a press-up. Repeat this two times. (Duration: 1 minute)

5. Run n the spot with a scissor jump very 75 steps. Repeat this 100 times. (Duration: 6 minutes)

Aides also told the outlet that he 'wishes to continue' with the 5BX plan, an 11-minute workout.

It was originally designed to keep pilots in top shape, no matter where they are, as the exercise routine does not need any equipment.

The military routine features five exercises, as its name suggests, which include stretching to touch your toes, sit ups, press-ups and stationary running with scissor jumps.

Charles - who has served in the RAF and Royal Navy - is said to do this routine twice a day.

Mr Payne said: 'This is a man who for many years has begun his day with exercises set down by the Canadian Air Force. He generally consumes extremely healthy, organic food and doesn’t drink much alcohol.

'He is always out walking and the pace at which he moves is such that it makes it very hard to keep up with him. 

Charles Anson, former press secretary to Queen Elizabeth II, said the King would likely get a 'bit impatient' from the change in his schedule, telling Times Radio: 'He tends to work through the day and through much of the night.'

With a reputation as fit and healthy for his age of 75, Charles has kept active with hill-walking and gardening.

Queen Camilla has spoken of her husband's fitness before, during the pandemic, telling the BBC: 'He is probably the fittest man of his age I know.

'He'll walk and walk and walk. He's like a mountain goat, he leaves everybody miles behind'.

Even daring adventurer Bear Grylls described Charles as 'an adventurer at heart' and a 'champion of the outdoors' his entire life.

The King's love for the outdoors – including hiking and camping – is thought to have been fostered during his time at Gordonstoun School. Pictured in 2012

Studies have found people who get exercise during treatment not only deal better with side effects but also may live longer.

International guidelines recommend patients stay active and get back to their normal activities as soon as possible.

The King's love for the outdoors – including hiking and camping – is thought to have been fostered during his time at Gordonstoun School.