Towering over Mumbai is the world’s most expensive private residence. The 27-storey, $2billion Antilia skyscraper is home to India’s richest man, Mukesh Ambani, and his family. Like something from a James Bond film, the 400,000 sq ft building boasts a ballroom, three helipads, nine lifts and its own 50-seat cinema, as well as six floors devoted solely to storing cars. It reportedly takes 600 staff to keep it running.

Yet in its shadow, quite literally in some cases, are the biggest slums in the world.

Indeed, more than half the population of Mumbai, née Bombay, live in shanty towns that in many cases lack access to clean water, electricity and public transport.

And this, according to critically-acclaimed crime writer Vaseem Khan, is the striking paradox at the heart of India, which can be traced back to the days of the Raj.

The London-born author and university research manager, who takes the reins as programming chair at this year’s highly-anticipated 20th anniversary Theakston Old Peculier Crime Writing festival in Harrogate, admits: “It’s a controversial topic because virtually everything the British did in India was to smooth the rails for their own colonial enterprise.

“They built the railways to move men and material around the country, they taught the language so the Indian Civil Service could work more smoothly, and they introduced the legal system to mirror their own.

“For Indians, none of those things justify colonialism, but some feel they later made it easier for India to become a modern, semi-Westernised and globalised economy.”

Having enjoyed an economic boom from the outsourcing revolution – hosting call centres and other back-office functions, taking advantage in part of the ubiquity of the English language – India nows enjoys a burgeoning middle-class.

Mumbai, the country’s de facto financial hub, is one of the world’s wealthiest cities.

Yet like Antilia, the shadow of Empire towers over Vaseem’s delightfully witty and page-turning Bombay-set Malabar House novels, featuring India’s first female detective Persis Wadia and Met Police criminologist Archie Blackfinch.

Making sense through his fiction of the fallout from the August 1947 Partition of the continent into Muslim Pakistan and Hindu-majority India – costing a million-plus lives to inter-communal violence – has become something of a speciality.

“I have this line I use: ‘Not every Briton that went to India was a sinner, and not every Indian was a saint’,” Vaseem continues. “What that means to me was that there were plenty of Brits who went out there to earn a crust. They weren’t all Clive of India.

“Many were ordinary folk who qualified and were told there was a job in the Indian Civil Service. They did what many normal people do to this day – they travelled across borders to earn a decent wage.”

His award-winning series, beginning with Midnight At Malabar House, entertainingly explores a country finding its way in the post-colonial era.

The writer, whose long journey to publication began, aged 17, with a Discworld homage inspired by the late Terry Pratchett, feels a special affinity for the period.

His father was born in the Punjab and, as a boy, forced to flee India for Pakistan as Partition tore the subcontinent apart. “His family was part of the post-Partition migration and thankfully he missed most of the violence. But there were stories about friends and family losing everything, even dying,” says Vaseem.

“It was a nightmare of a time. It was so dark, and so much blood was shed, that shadow has lingered for 76-odd years now. One million Indians were killed but they were killed by other Indians: Muslims and Hindus and Sikhs fighting each other.

“The Brits bungled Partition – they didn’t supervise it, they did it too quickly, and the people involved, Lord Mountbatten and Cyril Radcliffe [whose line splitting the new countries was far too arbitrary] – were culpable in that sense. But the actual killing was by Indians.

“That’s what I mean when I say that not every Indian was a saint in this story of the end of the Raj and the beginning of Indian independence.”

Having married and moved to England, Vaseem’s father worked as an industrial baker in East London and brought up Vaseem and his four siblings.

After graduating from university, the author, now 49, spent a decade living and working in India, where he met and married his Indian wife Nirupama.

“I went to Mumbai at the age of 23. The country I saw, this modern India, was incredible, having gone from an agrarian, pre-industrial economy to the near global superpower we think of today,” he explains.

“After spending ten years there and having returned to the UK, I wanted to write about modern India which I did with my first books – the Baby Ganesh Agency series.

“Then I started thinking about where this country came from and, for me, those roots were established when the British left.

“That particular period in India, just a few years after Independence and Gandhi’s assassination and the horrors of Partition, has not been well explored in fiction and certainly not in crime fiction.”

His subsequent Malabar House series introduced female detective Persis and Bombay’s smallest police station – home to the “misfits and rejects” of the Indian Police force, and expendable enough to handle the “hot potato” cases no one else wants.

The books have drawn complimentary comparisons to Mick Herron’s Slough House spy thrillers, currently starring Gary Oldman in an Apple TV+ adaptation. “Think Mick Herron in Bombay,” promised one critic.

Just published in paperback, the third book is The Lost Man Of Bombay.

Typically gripping, Persis and Archie investigate the murder of a white man found frozen in the Himalayan foothills near Dehradun.

“The idea came from the story that the first person who may have summited Everest was not Edmund Hilary but George Mallory, who died in 1924,” Vaseem explains.

“His body was found in 1999 and nobody knows if he was on the way up and had died before he made the peak, or had summited successfully and was coming down.”

A fourth novel, Death Of A Lesser God, focusing on Britons who stayed on after Independence, will follow in August. In the meantime, Vaseem is preparing for the world-famous Theakston Crime Writing Festival in Harrogate as its first Anglo-Asian programming chair. Taking place from July 20 to 23 at the North Yorkshire spa town’s Old Swan Hotel, where Agatha Christie famously reappeared after going missing for 11 days in 1926, the festival holds special significance.

“It’s a fantastic honour but it’s also a marker of how far the industry has changed certainly in the almost ten years since I was first published,” says Vaseem.

“When I came into the industry you could count the number of non-white crime writers with any traction on one hand. For me in particular, Harrogate resonates because when I was young our favourite TV show as a British Asian family was Agatha Christie’s Poirot series starring David Suchet.

“Even my father, whose English wasn’t great, would sit down and enjoy this show. Neither of us could have dreamed that decades later I’d be chairing a festival so closely linked to the Queen of Crime.”

Jack Reacher creator Lee Child and his brother Andrew are among a stellar line-up, including Lisa Jewell, Ruth Ware, Ann Cleeves, Jeffery Deaver, Lucy Worsley, SA Cosby and Chris Hammer.

The Daily Express is a media partner for the prestigious Theakston Old Peculier Crime Novel of the Year, for which Vaseem’s historical thrillers have previously been shortlisted.

The keen cricketer, who plays for Redbridge CC and The Author’s XI, an amateur club founded in 1891 by, among others, Sir PG Wodehouse, Sir JM Barrie and Sir Arthur Conan Doyle, revived most recently in 2012, uses his fiction to “correct” historical inaccuracies.

“I don’t really subscribe to the idea of tearing down statues,” he smiles. “I’d rather tear down people’s ignorance, and I don’t think you can do that if you start erasing history.

“You can only do that if you talk about history, good and bad.

“For instance, in Midnight At Malabar House, I talk about the Indians who invented the fingerprint classification system – Azizul Haque and Hem Chandra Bose. Credit went to their supervisor.

“Equally, in The Lost Man Of Bombay, I talk about George Everest who worked in India as a surveyor but had nothing to do with determining Everest was the highest mountain on earth. That was Indian mathematician Radhanath Sikdar, but the Royal Society wanted to honour Everest for his lifetime of work.”

Persis herself came about as a way of avoiding the typical hard-drinking, misanthropic detectives that populate much of crime fiction. “I’m a great fan of the maverick male cop who’s three times divorced and goes around disobeying everyone and trying to get the job done,” Vaseem smiles.

“In a way, Persis is the same. Sometimes skirts the niceties and she’s very blunt.

“But I needed an intriguing protagonist in an era when India was a very patriarchal society and its police known as insular, a little corrupt and certainly quite misogynistic.

“Many of the things I write about have parallels in the modern world.

“We’re still having discussions about misogyny in the police force – in Britain, too, as we’ve seen with Louise Casey’s bombshell report into the Met this week.”

Vaseem is yet to meet India’s real-life first policewoman, Kiran Bedi, 73, but has benefitted from the experiences of another ex-Indian cop, Jyoti Belur, a colleague at University College London’s Department of Security and Crime Science.

“Obviously she operated in modern India but, like Persis, she had the khaki uniform and a revolver and many of the issues she faced were the same.”

He also uses Persis and Archie as a way of examining his own heritage and the new relationship between the two nations: “Persis is an Indian who’s gone through the struggle and her co-investigator Archie Blackfinch is English.

“There is something metaphorical about their relationship, and it’s not always smooth sailing. History is always demanding we take sides, but as writers we have to try and achieve balance.

“I can be equally hard on Britons and Indians. I feel I can straddle both cultures.”

Has he been too kind to the British in the books, I wonder? “I’m interviewed regularly in India and no one’s ever suggested that, I think partly because every single one of my books begins with a white person being killed!” he smiles.

“I went to India in 1997 with my boss in England, Terry Brewer, a lovely gentleman from Kent with snowy white hair. After a few months in India, he joked: ‘Vas, something’s wrong, everybody’s so nice to me. Don’t they know what my forebears did out here?’

“But because India is full-steam ahead into the future, they don’t dwell too much on the horrors of the period. They have an enormous fondness for English people who come to India and engage with them.”

• The Lost Man of Bombay by Vaseem Khan (Hodder, £8.99) is out now. Visit expressbookshop.com or call 020 3176 3832. Free UK P&P on orders over £20. The Theakston Old Peculier Crime Writing Festival takes place July 20-23. Tickets will be on sale from May 2. Visit Harrogateinternationalfestivals.com for more information