The servant is back - and not just on the set of period television dramas such as Downton Abbey. A new study has uncovered the startling fact that there are more servants now working in London's Mayfair than there were 200 years ago. The survey - by Wetherell, an estate agent catering to the international super-rich - has revealed 90 per cent of the 4500 people who own houses, and 80 per cent of those with flats, have their own servants. In 1790, there were only 48 servants living in Mayfair and working for its 1500 residents.
And it's not just Mayfair. The number of domestic servants is booming across central London: wherever the multiple between the wages of the rich and the poor grows, so does the number of servants. Much of the time, the towering Georgian and Victorian terraced houses of Belgravia now have only servants living in them - their masters and mistresses are drifting around the world, from yacht to schloss to Park Avenue apartment, in search of pleasure or tax avoidance. Drive round the area at night, and it's often only the lights in the attics and the basements - the servants' quarters - that are on.
But the service industry isn't flourishing just in the gilt-edged parts of Britain. According to the Work Foundation, there are now more than two million part-time or fulltime domestic workers across the country. All told, 10 per cent of households now employ some sort of domestic help.
The nature of this new servant class, however, has changed drastically. Since Downton and Upstairs Downstairs days, the old fleets of country-house staff have all but disappeared. The modern servant now falls into two groups - the part-time cleaner, nanny or au pair for the middle classes; and the live-in house servant for the urban mega-rich.
In many ways, this represents a return to relative normality. The 20th-century culture of housewives doing everything for themselves - armed with an avalanche of labour-saving devices - was a brief blip in British history when servants went out of fashion. From the Middle Ages until World War I, whole armies of traditional servants were employed in this country. One of the reasons the castles and country houses of Britain were so huge was that they were designed to accommodate a vast staff. When Sudeley Castle, in the Cotswolds, was built in 1442 there were two big courtyards - one for Lord Sudeley and his family, the other just for his servants.
For the next half a millennium or so, domestic servants were run of the mill, not just for peers of the realm but also for the lower-middle classes. In 1851 there were 115,000 women aged between 15 and 20 living in London and the suburbs; 40,000 of them were in service. Whole industries were built on the back of these domestic arrangements: John Betjeman's ancestors ran a family company that made tantaluses - lockable drinks cabinets to keep servants from the sherry.
In the 1892 comic novel, The Diary of a Nobody by George and Weedon Grossmith, even Charles Pooter, a humble City clerk in north London, had a maid. The Pooters, like most people in Britain then, rented their house in Brickfield Terrace - but, still, it was a six-room house, "not counting basement", with the servant sleeping up in the attic.
The war brought an end to all that. Between 1911 and 1921, the number of servants in London's commuter belt fell by half. The size of households began its downward slide, too - in 1842, the average Victorian home contained 5.8 people, compared with 1.9 now.
This great decline in domestic service through the 20th century was partly a function of technology - who needs a maid to make a fire when you can flick a switch? But servants also became too expensive to employ. Mr Pooter would have had to pay negligible tax on his clerk's income, and could have got away with paying his maid a pittance. But, when taxes started to rise, economies had to be made.
The other death knells for domestic service were rising home-ownership rates, and house prices. In 1914, the pattern of house ownership had barely changed since feudal times: only one in 10 people owned their home. Domestic service - with the bonus of free accommodation - had obvious attractions. Between the wars, the number of home owners went up fivefold, and a million council houses were built: at last, Mr Pooter's maid could move out of her attic. World War II, and the Attlee government after it, brought an even bigger public housing boom.
Since then, increases in house prices have long outrun earnings, meaning there's not much left over for the middle classes to pay for a live-in servant, once they've bought their house. That's why you end up with that first, new expanding group of servants: the part-time hired hand, usually employed by double-income couples. For professional and family life to run smoothly, there is an increased reliance on external staff - since the new aspiration is to be time-rich, not money-rich (although the first tends to require the second). And the best way to become time-rich is to hire someone to share the load.
Yet a more transactional approach to domestic service also has its cost - particularly when it comes to the new generation of fulltime urban servants. In 2010, Prince Saud bin Abdulaziz bin Nasir Al Saud, a grandson of Saudi Arabia's King Abdullah, murdered his servant, Bandar Abdullah Abdulaziz, strangling him in the Landmark Hotel in Marylebone. In the build-up to the killing, the prince had beaten him up on regular occasions.
And it's not just the super-rich who give their servants a hard time. According to the charity Anti-Slavery: "Slavery still exists in 21st-century London, with an estimated 5000 people trafficked to the UK at any one time. While some are forced into prostitution, increasing numbers are forced to work in construction, domestic work, cleaning, the restaurant trade, care, on farms and in factories."
This month, three people were convicted at Croydon Crown Court for beating, raping and threatening to kill a woman who had come from Hyderabad to work as a nanny in Edgware, only to endure three years of slavery. Once she arrived, she had her passport confiscated by her first employer, was raped by her second and burned with an iron by the third.
Long gone, it seems, are the days of paternalism and noblesse oblige. Mary Poppins and Downton Abbey may give a pretty, rose-tinted vision of back-breaking life below stairs - but perhaps the old-fashioned servant's life wasn't so bad after all.