The Queen and Prince Philip board a plane in Australia. Photo / Getty Images
Queen Elizabeth II, officially the most widely travelled head of state in history - if anyone has a polished coping strategy for jet lag, surely it is she.
Perhaps surprisingly it's barley sugar, sold in the form of boiled sweets, along with unspecified homoeopathic remedies, according to an interview conducted many years ago by The Independent.
It's a curious revelation, the Telegraph revealed Her Royal Highness' other travel habits and unearthed a gold mine of surprising factoids.
1. Barley sugar, really?
This one's a head-scratcher, but given the number of air miles the Queen has clocked up and her ability to avoid nodding off mid-state dinner, perhaps there's something in it.
We asked GP Dr Nick Knight, who has a specialist interest in lifestyle medicine, to shed some light.
"Carrying out your daily habits like eating and sleeping in line with your new destination's time zone - both en-route and on arrival - helps re-synchronise our body clock to our new environment," he says.
"What the Queen is doing by having barley sugar is essentially using her body's sugar metabolic pathways to help adjust her body clock. It is a little niche but essentially the same should happen if you were to have your breakfast, lunch and dinner at times that match your destination before you get there, regardless of whether you're hungry or not. Doing this instead of just consuming barley sugar will obviously be more filling."
2. A black outfit, always
The Queen travels everywhere with at least three outfit changes a day, all numbered and packed in steel wardrobes on wheels, along with one all-black ensemble for the purposes of mourning, just in case. She learned this one the hard way.
When the Queen was informed of the death of her father King George VI on February 6, 1952, she was in Kenya. During her flight back to London it was discovered that she only had a floral dress with her to wear. Her aircraft was thus grounded upon arrival in London until a black dress could be delivered on board, which she changed into before disembarking.
3. A sizeable entourage
According to the Telegraph's Royal correspondent Gordon Rayner, the Queen's travelling entourage typically runs to 34 people, who will include staff from the Master of the Household department, to oversee catering and logistics, her private secretary and his deputy, a secretary for each of those secretaries, two secretaries for the Duke, two dressers, a hairdresser, a valet, two ladies-in-waiting, an equerry for military liaison, press officers, eight police bodyguards. the Foreign Secretary and his or her staff.
4. A supply of her own blood
A Royal Navy doctor also accompanies the Queen on tours, having researched the nearest hospitals in advance. In countries where a reliable blood supply is questionable, the Queen and the Prince of Wales both travel with their own personal packs of blood following in their convoy wherever they go.
Their doctor is never more than a few paces away, carrying a bulky medical bag containing a mobile defibrillator and all manner of emergency medicine.
5. A monogrammed kettle
Home comforts are of great importance, as evidenced by the monogrammed kettle and Earl Grey tea the Queen takes with her around the world. She also travels with her own hot water bottle, pine-scented soaps, framed family photos and Harrods' sausages.
6. Flying commercial? No thanks
In 2002, Prince Philip announced to the Aircraft Research Association: "If you travel as much as we do, you appreciate the improvements in aircraft design of less noise and more comfort - provided you don't travel in something called economy class, which sounds ghastly."
The Queen is in fact the only Royal Family member who doesn't take scheduled flights at all. The rest of the family do though. While their preferred airline is British Airways (the Duchess of Cambridge flew to Rotterdam in 2016 in BA seat 1A), the Duke of Cambridge was spotted on a flight to Glasgow with Ryanair in 2015, and Prince Harry flew economy from Memphis to Dallas on American Airlines in 2014.
Incidentally, the Queen's heirs must ask her permission before boarding a flight since, according to Royal protocol, no two heirs should fly together. This is in the event of there being a fatal crash, and one or more successors to the throne being killed at once. She has been known to bend the rules however, having permitted Prince George to travel to Australia and New Zealand in 2014 with his parents when he was nine months old, for example.
7. Easy on the exotic spices
The Master of the Household department will be in the reconnaissance party to tell foreign chefs not to cook anything with garlic or too much spice for fear of giving the Queen bad breath, and not to cook shellfish or anything that could cause food poisoning. (The Queen likes fish and poultry but has never divulged what her favourite meal is, because, as one of her staff told Rayner, "If she said she had a favourite meal, she would never get served anything else.")
8… but bring on the gin
The Queen's favourite drink of all is gin, mixed with a splash of Dubonnet fortified wine and a slice of lemon - pips removed - according to personal chef Darren McGrady. She is said to enjoy one every day, and that goes for trips abroad too. For security reasons, the wherewithals to craft this tipple are packed along with the rest of her belongings.
Royal tours are choreographed to the minute, whether it be the exact time the Queen sits down to dinner or the precise moment she gets into a car, as set out in an old-fashioned spiral-bound pocket itinerary carried by each of her aides.
10. Special loo roll
For toilet breaks a retiring room is designated for the Queen and the Duke of Edinburgh everywhere they will visit, which may also be used as a panic room in case of an attack. One former aide told Rayner: "Hosts spend more time worrying about the loo arrangements than anything else, down to what colour the towels should be and whether the loo roll is a suitable brand."
11. The ultimate travel wardrobe
The Queen's senior dresser, Angela Kelly, travels abroad weeks or even months in advance to make sure that the outfits she has in mind do not clash with backdrops. In the interests of modesty, weights are sewn into the hems of skirts and dresses should a sudden gust of wind strike as she boards and disembarks planes.
Her hosts are also known to go to extraordinary lengths to keep Her Majesty comfortable. As revealed in 2015's 'The Wicked Wit of Queen Elizabeth II', by Karen Dolby: "Once in Nigeria her hosts, anxious to keep her cool, turned up the air conditioning in her rooms so much that her clothes froze on their hangers."
12. All aboard, corgis
The Queen's devotion to her corgis seemingly knows no bounds. She's owned more than 30 of them during her reign, although she stopped breeding them in 2015 on the grounds that she didn't want any of them to survive her. At last count she was down to just two, Holly and Willow.
Wherever possible, Her Majesty travels with her hounds - she even smuggled one of them along in the car when she and Philip set off on their 1947 honeymoon in Hampshire. They also fly with her up to Scotland and back on a regular basis.
The Queen is the only royal who doesn't require a passport, given that the British passport is issued in her own name. She does still have to pass an identity check every time she leaves or re-enters the country, which requires her to provide her full name, age, address, nationality, gender and place of birth to immigration officials.
14. No moaning
Rayner, who has accompanied 20 Royal tours over the years, indicates that as travel companions go, you won't find a more committed voyager.
"The Queen's work rate remains ferocious, particularly so for a woman of her age," he writes.
"Naturally, [she] would never dream of complaining, and toughs it out even when she is feeling ill."