Just what do the rich and famous get up to behind closed doors? Simeon Rosset knows more than most.
A modern-day equivalent of Downton Abbey's Mr Carson, Simeon has worked for nearly 20 years as a butler serving a galaxy of stars, royalty and the odd billionaire.
The 37-year-old, from Kent, has spent much of his working life in castles and palaces and on superyachts and shooting estates.
He's provided services at house parties and gala dinners to celebrities such as Kylie Minogue, Bono, Quincy Jones, Cliff Richard, David Beckham and Cilla Black.
But for Simeon, who now runs Scotland's only training academy for butlers, there's one star who stands out.
"Of all the different celebrities and stars I've met, I've never met anyone with quite the personal aura of Pavarotti," he says.
The Italian opera singer, who died in 2007, was widely regarded as one of the finest tenors of the 20th Century, and one of the most successful.
Simeon says: "I was his personal butler while he was performing in Kent in 2004, and he was this incredible megastar.
"He had a complicated rider, a list of requirements - as most celebrities do - because these things progress as they get through their levels of fame.
"But once we got everything in place, he wasn't difficult to look after at all."
Simeon says Pavarotti was "very down to earth".
He says: "What he enjoyed the most was to sit down and have a game of cards with his old school chums - people he had been friends with for 60 years who would accompany him on his tours.
"That was his absolutely favourite way of spending an evening."
Simeon is used to dealing with strange requests from celebrities, which he says can involve something as simple as a particular mineral water, or as "complicated" as finding rare flowers.
One guest, he says, wanted six roast chickens available to them at all times.
"As a butler, one thing you don't do is say no to the guests," he says. "Whatever they ask you for, you find a way of getting it for them, as long as it's legal.
"I remember one time a client in London wanted these very specific tomatoes from Italy for dinner that day.
"So we actually sent a private jet to Modena to pick the tomatoes up and bring them back.
"In effect, they were worth thousands of pounds - perhaps tens of thousands of pounds - each."
Butlers such as Simeon are in high demand these days, according to the International Butler Academy in the Netherlands.
It says the number of butlers worldwide has increased rapidly in the past 10 years, with up to 2.5 million now in employment, including those working in the hospitality industry.
The academy's chairman and chief executive, Robert Wennekes, explains: "Never before in history have there been so many wealthy and ultra-wealthy people as today.
"These people own great estates and require the services of professional private staff to manage their properties, and in general to be of service."
The academy estimates that a butler with five years' experience can earn about US$70,000 (£50,000) a year, while the most experienced can earn $100,000-plus (£70,000).
So what exactly is the role of a modern day butler?
Simeon explains: "Most butlers are still live-in staff.
"Strictly speaking, he or she looks after the house - the household staff, the meals, the silver etc.
"A valet, on the other hand, is more in the Jeeves style - looking after a person's sartorial needs, doing the ironing and even dressing them.
"Then there's a housekeeper, who is more based around the bedrooms - more about changing the linen, looking after a team of staff, the cleaning, the running of that side of the house.
"But the roles have become quite blurred, much more than they ever have before."
According to Simeon, a butler must be able to turn his or her hand to almost anything.
"Modern butlers, or as they are often called house managers these days, can expect to carry out any role - from booking a private jet charter, to cooking, shopping, polishing shoes, cleaning, handling financial accounts and even supervising the building of someone's house."
Handling security is often a part of the job.
"I have done some bodyguard and anti-terrorism training because we are quite often working in a preventative manner," he explains.
"We make sure that our guests don't take the same routes to and from places that they go regularly, make sure that we use a pseudonym for restaurant bookings and things like that so the wrong people don't get a heads-up."
So what does Simeon think makes the perfect butler?
"A really good butler should almost never have to be told anything, because they've already done it before being asked.
"For example, if you are looking after a couple, and they are going out to dinner that night, you can probably assume that they won't be waking up early the next day.
"They will probably want lunch late so they don't get too hungry before their dinner - obviously you will already be arranging all the transport and things like that for them so you can pre-empt things."
Simeon says discretion is all important in the relationship between a butler and a client.
"You probably know your client better than anybody else knows them.
"But it's very important that you don't consider yourself their friend, because you are not - you are a professional doing a job and you have to keep professional at all times.
"It's also a huge responsibility, because you know every detail about their life - and of course they would not want you to share any of those details, even inadvertently in a conversation with someone."
Simeon has been passing on his knowledge to dozens of students at his butler academy in Paisley for the past three years.
His courses include the practical stuff, such as silver service training, house management, etiquette and protocol.
But he also places emphasis on posture and dress code.
"The way you stand and present yourself to a client says everything in the first 30 seconds.
"If you look like someone who's slouchy and lazy, they will assume that's what you are like - even if you are actually a very hard worker.
"We are often not in the full morning suit and when that's the case, you have to put a lot more thought into it.
"If you are wearing chinos and an Oxford shirt, which is often the unofficial uniform of a butler, it has to be a very well ironed shirt, you have to have very good creases in your trousers and you have to have nicely polished shoes."
Students to his academy come from a cross-section of society, according to Simeon.
"I had one chap who had been a successful solicitor but wanted to retrain as a butler.
"People have come from Beijing, Dubai, Bangladesh and Budapest - all with different backgrounds and different ideas."
He's trained a couple of women so far in the role and is keen to see more come forward.
"I've been really actively encouraging ladies to become butlers because they are equally good, equally skilled and there's literally no reason for them not to be."
Simeon hopes to pass on his enthusiasm to those interested in joining the occupation.
"I have served dinner halfway up mountains, I've been on superyachts, I've been to half the Mediterranean enjoying wonderful locations, and met some incredible people.
"It's the variety that makes butlering so great because you never know what you are going to do."